When an actor plays the same role on television for 10 years, it typically defines — and limits — his career forever. In David Schwimmer’s case, the part of Ross on “Friends” was both a validation and an opening.

“When I first came out to L.A. after college [at Northwestern University],” Schwimmer recalls, “I felt like I was getting a lot of feedback in auditions: ‘He’s really good, but he’s a little too ethnic.’ I’d be like, ‘You mean Jewish. What are you talking about? You’re saying I’m a Jew, so I can’t play the lead?’

“I kept thinking, ‘Well, dammit, Dustin Hoffman has a pretty great career. Elliot Gould had a pretty magnificent career. Well, screw it. I’ll find the right role someday.'”

Indeed, Schwimmer did — on “Friends,” which ended its run in 2004. Along with showcasing his talent, the sitcom paid very well, helping Schwimmer support the Lookingglass Theatre he co-founded 20 years ago in Chicago with a group of fellow Northwestern grads.

Now, just north of 40, Schwimmer’s career is heading in multiple directions — without any “Friends” baggage to slow him down. First out of the gate is “Run, Fat Boy, Run,” a slight, genial comedy set in London that marks his feature directorial debut.

“Run, Fat Boy, Run,” which stars Simon Pegg (“Shaun of the Dead”) as an immature underachiever who runs a marathon, opens March 28.

Although the movie is forgettable, Schwimmer is anything but a lightweight. He’s got terrific dramatic chops, as he regularly demonstrates onstage and confirmed in “Uprising,” the 2001 NBC miniseries about the Warsaw Ghetto.

For the most part, filmmakers have ignored that talent, although he’ll be seen this fall opposite Kate Beckinsale in the Washington, D.C.-set political thriller “Nothing But the Truth,” and he had a memorable role as Capt. Herbert Sobel in the 2001 HBO miniseries “Band of Brothers.”

“There are several films I’ve done that are more dramatic,” Schwimmer hastens to point out in a recent interview during a San Francisco publicity stop. “I got to do this movie ‘Duane Hopwood,’ but it didn’t get a real release. I’m not overly worried about it. I feel like I’m in it for another 40, 50 years. I tend to feel secretly, ‘They’ll come around. They’ll get it. They’ll understand one day.'”

He smiles, and adds. “But maybe I just have to tell myself that.”

Schwimmer was born in New York and grew up all over Los Angeles. After his bar mitzvah, he attended Hebrew school twice a week for all four years of high school. Unlike many Jewish actors or directors, though, he doesn’t include any classic Jewish characters or overt Jewish themes on his list of dream projects.

“I feel like it’s not something that I have to explore or express in everything I do,” he muses. “I’m developing a couple of things, but it’s kind of not relevant whether the main character’s Jewish or not. Although I’m very sensitive to it, I have to say.”

As an example, he cites one project he’s working on: a thriller about a pedophile. “There’s no way in hell I’m going to make him Jewish, or cast a Jewish person in it,” Schwimmer says with a husky laugh. “We’ve got enough that we’re fighting against, enough stereotypes.”

The project reflects Schwimmer’s efforts to educate people about sexual predators — he’s long been involved with the Rape Treatment Center of Santa Monica — but it’s just one of several social issues he’s committed to. He spent three years adapting Studs Terkel’s “Race” for the stage, and directed it at Lookingglass.

“That was about exploring the issue of not only race but ethnicity,” he declares. “For me, it was very much about my own relationship to being a Jewish man and growing up and having incidents of racism or prejudice, and constantly thinking about it.”

Needless to say, Schwimmer will never abandon comedy. He will provide the voice for Melman, the hypochondriac giraffe, this winter in the animated sequel “Madagascar: The Crate Escape.”

So what defines Jewish humor?

“I don’t think I’ve really sat down and thought about it, but I feel like it’s kind of philosophical, in that there’s a worldview about being fatalistic,” Schwimmer says, thinking out loud. Then he tells a good news-bad news joke involving a doctor and patient to illustrate his point.

“It’s all bad news,” he says with a wry smile. “You try to make the best, but it’s all bad.”

“Run, Fat Boy, Run” opens March 28 at the Bridge Theatre in San Francisco.