Julia Roberts is one of those few actors who have achieved a stardom that never really fades: She’s always up there in the pop-culture firmament, flashing that famous smile. So it comes as a bit of a surprise to learn that her role as the Watergate whistleblower Martha Mitchell in the new Starz mini-series “Gaslit,” which premieres April 24, is her first acting work in four long years. As if making up for lost time, Roberts has found in the part of Mitchell — wife of the former attorney general and Nixon confidante John N. Mitchell, played in the series by Sean Penn — a character that affords her the opportunity to deliver the full Julia experience. Martha’s brighter moments give Roberts the chance to exude the charisma and sass that lit up her earlier, lighter movies. Then as the story slides into grimmer territory, she draws on the darker, more fine-grained character work that has defined the later years of her career. It’s a welcome return. “It wasn’t by design,” Roberts, who is 54, says about her recent low profile, “so much as not finding something that I was interested in. I was surprised how quickly the years seemed to go by.”

The story of Martha Mitchell is largely about power and influence and how men react to a woman trying to exert it. You’re someone who has experienced having power in your world. Did you bring any of that to Martha? I guess I could find commonality with Martha in that on the surface she’s a woman who’s sure of herself and comfortable around all the gents and cigars and knows how to work a room. What’s interesting is that her undoing, in my thought process in portraying her, was that she didn’t want to go out and beat the drum for Nixon, but people responded to her. So she was pushed to go out and represent Nixon, and I think she started to dig it. But it wasn’t without an enormous amount of cajoling. She had problems with her nerves and anxiety and being in front of people, which I can completely appreciate — you have to conceal all that. I don’t know if that answers your question. I feel like ultimately I could appreciate her more than lend myself to her.

The thing about your answer — My rambling? [Laughs.]

You can ramble. It’s fine. But you skipped the part of the question that alluded to your experience of power. OK, what is my experience of power? Well, it’s always going to be the person, man or woman, who doesn’t know what they’re doing or doesn’t have confidence in what they’re doing that’s going to be the pain in the ass. Even when I am for sure not the smartest or most powerful person in the room, if I feel confident being in that room then I feel good saying, “I’m sorry, what are we doing?” That becomes collaboration, which is my favorite thing. Sam Esmail, he’s a great collaborator because he brings in such a strong team, and goodness knows I have waited my adult life to work with my friend Sean Penn. The John and Martha scenes, when we first read them, Sean and Matt Ross came over to my house, and I made lunch, and I said to Sean, “I don’t know — the kind of actor I am — that I could perform these scenes with someone that I didn’t know very well.” Because it’s tricky stuff. Especially when you start hitting each other. I’m not a method actor, but someone hitting you is someone hitting you.

What kind of actor are you? If I had just met someone and we’d had a week of rehearsal and then started these scenes — I’d be curious to see how that performance would have ended up. The first day that Sean filmed, our characters are coming into a hotel from an event. We’re all dressed up and we walk into this room and we realize that the Secret Service guy is there. He says, “Mr. Mitchell, I need to speak with you” or something. It’s pretty straightforward. But Sean goes, “I have an idea. Trust me on this.” So we go outside the door, Matt says “action” and Sean gets on his knees behind me. He’s got his hands on my hips, and he’s going “Rawr rawr rawr rawr” into the back of my dress as we come into the room. Only a pal could be that crazy off the bat. It can’t be, “Nice to meet you; I have an idea!”

When I asked you about parallels between yourself and Martha Mitchell, you said you could “appreciate her more than lend yourself to her.” It occurs to me that when I went back to old interviews you have done, you often seemed resistant to making links between yourself and your characters. Is that because you don’t think of acting — as many people do — as this process of pulling from one’s innermost experiences and emotions? Or maybe is it because you have an aversion to talking about your internal self with journalists? If it comes off as resistance, I think it’s because you’ve been doing a deep dive on me. So hearing me say whatever it is I’ve said before might feel like I’m making a big point when they were just a smattering of small points. But if I were to examine this as you’re asking me to, to say that too much comes from inside me is to negate all the hunting and gathering I’m doing to create something. I want to find things and examine outside myself and make things up. Because once you start the performance, that stuff that’s inside us, that alchemy that makes us individuals, that’s always going to bubble up to the surface in whatever way it needs to.

“Gaslit” is another of these emotionally heavy ensemble pieces that you’ve done over the last 20 or so years. But before that you were doing more persona-driven, romantic-comedy star vehicles — movies that called for a different kind of acting than “Gaslit” or “Ben is Back” or “August: Osage County.” Did the move toward heavier material make you think differently about the kind of actor you are or can be? What I’ve learned is that you always want to do what you’re not doing. Whenever I’m in a comedy, I think I just want to be at a table with a cup of tea sobbing over something. Then you’re doing that, and you think, Oh to be wearing a pretty dress and laughing. People sometimes misconstrue the amount of time that’s gone by that I haven’t done a romantic comedy as my not wanting to do one. If I had read something that I thought was that “Notting Hill” level of writing or “My Best Friend’s Wedding” level of madcap fun, I would do it. They didn’t exist until this movie that I just did that Ol Parker wrote and directed. But even with that, I thought, Well, disaster, because this only works if it’s George Clooney. Lo and behold, George felt it only worked with me. Somehow we were both able to do it, and off we went. To go from John and Martha Mitchell, to play these scenes with the greatest dramatic actor, I think, of my generation in Sean Penn, and then run around Australia with George playing these very funny scenes — I’m living my acting dreams.

You’re telling me you didn’t do a romantic comedy for 20 years because there wasn’t a single good script? Not one? Yeah. It can’t be 20 years, can it?

It is. What was 20 years ago?

That was around the time of “America’s Sweethearts.” You also did those Garry Marshall movies but your parts were small. Here’s the thing: If I’d thought something was good enough, I would have done it. But I also had three kids in the last 18 years. That raises the bar even more because then it’s not only Is this material good? It’s also the math equation of my husband’s work schedule and the kids’ school schedule and summer vacation. It’s not just, Oh, I think I want to do this. I have a sense of great pride in being home with my family and considering myself a homemaker. For so much of my children’s younger life they would see their dad go off and I would work a little, but they almost didn’t notice. It was like I was only gone when they were napping or something. But as they get older, and particularly with my daughter, I do have a sense of responsibility for showing my children that I can be creative and that it’s meaningful to me — so meaningful that for periods of time I will choose to focus on that almost more than my family, which has been hard for me to come to terms with. I almost didn’t do “August: Osage County” because they were going to start filming right as our youngest son was starting kindergarten, and I was like, How could I miss this? I remember talking to Danny about it, and he said: “At some point you were going to have to leave us to work. Wouldn’t you rather roll those dice in a situation like this, where you have a good understanding of what you’re going to be doing and the people you’re going to be working with?” He was right to push me, because if he said, “I don’t know,” I would have been like: “I don’t either! I’m not going!” That’s the female plight. That feeling of leaving is hard.

What about from a business perspective rather than a family perspective? How do you decide whether the moves you’re making are the right ones? I’ve never put the work in a place of, “Doing this part, what will people think?” I read it. I want it or I don’t want it. That’s how I’ve made my decisions for 50 or whatever movies.

But was that the case with movies like, for example, “Mary Reilly’’ and “Michael Collins,” both of which were seen as an effort on your part to break out of some typecasting and both of which didn’t do well? You’re saying they had no bearing on the choices you made after? You weren’t then gun-shy or looking for roles in which you would be more secure? No. Your performance, obviously there are people helping you accomplish this goal. But the further away you get from it, the more you look alone. When you’re alone out there in the world — the “Mary Reilly,” 100-years-ago world — you look at that performance, and you think, I am fully responsible for it. I have to be fully responsible for my decision. You say “Mary Reilly” to me today, and I mean, I’m not half bad in that movie! I think I got short shrift. I can stand next to it happily because it was my decision. I feel that way about everything: Do I want to be that person who can stand next to this forever? Because the sum of my joy is finished the day that we wrap. That’s all the fun I will have on a movie.

You’re basically saying you don’t want to make a turkey. Yeah, I don’t want to make a turkey. But if I do, I want to be able to go, That’s my turkey.

If a young actor or actress were to ask for advice about how to build a career or navigate Hollywood now, what would you tell them? My first response is don’t take advice from actors. Because everybody’s experience is unique — should be unique. Also, I am less qualified to give advice now because the business has changed entirely. It’s a little sad, because when I started, I felt like you did a movie and if it did well then you might get offered a couple of other movies and might have more choice and you’d get paid a little bit more on the next one. There were incremental shifts in opportunity, and it made more sense. Now it’s made more of air; maybe it doesn’t feel as sturdy when you’re going along. I felt pretty sure-footed about the choices I was making. You don’t have those incremental markers anymore, it doesn’t seem like.

So this new movie you’ve made with George Clooney: Was it easy to stretch the rom-com muscles again? The good news is yes. I love to laugh and be funny. You get into that mode of those endorphins going off when you’re clever and people going, “Oh!” Then that becomes this automatic thing where you’re always thinking in terms of creating fun. It’s a joy to play in that sandbox. It has been a long time.

Is it still possible for you to do the trademark Julia Roberts moves — the big smile and the big laugh — without any self-consciousness? If something’s funny, I’m going to laugh. If something’s not funny, nothing’s going to make me laugh. I would probably get a lot further in my career if I had more control over those things.

It’s true, you haven’t gotten very far. [Laughs.] Still!

Is it right that your smile is insured? No. What am I insuring it against? How would you do that?

I don’t know. I thought it was like how you hear that Tina Turner’s legs were insured. Oh, I have heard that. I mean, if my smile was insured, there would be someone at my house on a nightly basis saying, “You need to floss longer.”

It’s interesting for me to hear you talk about your smile because when I give my big smile, people say things like “Are you OK?” and “Have you seen a doctor?” [Laughs.] Oh, stop.

I’m told I mostly make up for it with my winning personality. Anyway, I asked earlier about the roles you’ve taken during the later part of your career. Are there personal reasons for why you’ve gravitated toward heavier stuff? I’m 54 years old. The truth of what you see and how you understand it and the weight of things becomes clear. You want to be able to unpack that. Also, it might be a response to having a happy life. You think, Why would I leave a happy life to go pretend to be in a happy life? You were also talking about me being more in ensembles: I haven’t put a geography map over the workload and seen where the borders are of what I’ve done. I bet in the analysis of it there’s probably equal amounts of two-handers, four-handers, six-handers, eight-handers.

Sorry, if we overlaid eight-handers on the geography map? I’m throwing out a lot of nomenclature here, David. Keep up if you can. [Laughs.] But what does it all mean? You tell me.

Well if you look at that map, you pretty much stopped doing big Hollywood star-driven lead roles after around 2001, 2002, and I’m curious about what drove that aside from family dynamics. Or let me put it to you this way: I interviewed Brad Pitt once. He, like you, had a similar demarcation line in his career, after which the roles changed. When I asked him about it, he said he had an epiphany on the movie “Troy,” when he realized that he couldn’t get out of the center of the frame and didn’t want to play the hero anymore. I’m wondering if you had any similar turning point? Um, no. But I do remember watching “Troy” and thinking Brad should not be the center anymore. I had that moment of clarity for Brad. For me, there might have been something subconscious. But I can’t say that I made a decision to do something different.

Going back to “Gaslit”: There has been this trend of retelling the stories of women who were harshly and quickly judged by the public in their time — people like Monica Lewinsky or Tonya Harding. Martha Mitchell’s treatment in “Gaslit” fits in with that redemption-narrative cultural theme. Were you thinking of her in those terms? And are there risks to interpreting a historical figure through a contemporary perspective? Martha could very much find herself in the same situation today as 50 years ago, left holding the bag and to have the whisper campaign against her: “She’s crazy. She’s an alcoholic.” There’s nothing that makes you look crazier than running around screaming, “I’m not crazy.” You say culture is quick to judge. Is anyone slow to judge? It doesn’t exist. So of course when given time to consider someone or a situation, nine times out of 10 you are going to reveal a gentler interpretation.

There’s also the issue of the gap between an individual’s self-perception and how they’re perceived by the public. What do you know about that gap? I decided a while ago that I’ll never really understand what people think about me and I don’t need to. I also feel like I’m a neutral person. I’m not one of those polarizing personalities — I don’t think. I don’t know. Because my job is so perfectly positioned in the priorities of my life, I’m not investing time in understanding the relationship between who I am and who people might perceive me to be.

Did you ever spend time thinking about it? Maybe when I was spending more time thinking about, Who am I? When I was 22 or whatever.

What were you thinking about who you were back then? In that period of time, particularly when I wasn’t working, I was not sure what I was looking for, but I was sure what I wasn’t looking for. At least I had that going for me. I could read a script and say, I am not looking for that. People often ask actors, What’s your dream part? I have no idea. I can’t conjure it.

That period of searching — was that connected to suddenly becoming so famous at such a young age? There was that too. But what that meant in 1990 is different than now. I mean, I’m not Grandma Moses, but there’s been so much innovation in these last few decades that put such a different shift on society and the way people communicate. It’s just different.

Let me ask: During one of these periods when you’re not working, when you’ve got downtime, what’s an ideal day? Oh, I don’t want to sound like a turkey. I could say it, and then people will either be like, “That’s sweet” or “Oh, [expletive] off.”

I thought you didn’t care what people think. I still have a beating heart! When people say “she’s this” or “she’s that” — that I can’t do anything about. But I don’t want people reading your nice piece that’s going to be so interesting and people are going to be like, “Wow, she’s interesting in a way I never realized” — it’s all on you, David — I guess it’s like when actors talk about their eating and exercise habits. There’s two people inside me: one that goes, OK, they look great. They eat these things; they don’t eat those things. Then the other part of me goes, “Oh, [expletive] off.”

This is a convoluted answer to “What do you do for fun?” [Laughs.] Well, I’ll tell ya. They say you’re only as happy as your least happy child. So when there’s harmony in the house and you get up and make breakfast and see everybody off to school. Then do some adventuring with my husband. We’ll take a bike ride or have a coffee or a meal somewhere, and then I’ll have time to myself and now it’s almost 3 o’clock. I’ll go get the kids from school. Lacrosse practice. Start making dinner. It’s boring! That’s why you want to go, “Oh, [expletive] off.” But it’s the joy of the details of life that I get to lean into because I have this cool job. If I was here for the last 18 years doing that all day, every day, it probably wouldn’t still have pixie dust on it. But I go away, and I miss it so much. Then I come back, and it kind of resparkles. I don’t know. I can’t be the kookiest person you’ve ever talked to, David. God knows, I cannot be!

This interview has been edited and condensed from two conversations.

Opening illustration: Source photograph by Shayan Asgharnia/AUGUST

David Marchese is a staff writer for the magazine and the columnist for Talk. Recently he interviewed Neal Stephenson about portraying a utopian future, Laurie Santos about happiness and Christopher Walken about acting.