Chicago native Johnny Galecki turned a one-time appearance on “Roseanne” into a five-year role, and has scored Emmy and Golden Globe noms for portraying Leonard Hofstadter on “The Big Bang Theory.” Next, he battles deadly technology opposite Aimee Teegarden in “Rings,” a reboot of “The Ring” thrillers out April 1. And he’ll star in, as well as exec produce, dramedy “The Master Cleanse.”

How did you grow as an actor during “Roseanne”?

That experience, from 16-21, I really consider my college in many ways. To work with Roseanne, who’s from the standup world, and John (Goodman), who’s a terribly disciplined film actor, I had the best professors in the business.

Why did you ask to play Leonard over Sheldon in “Big Bang”?

It was a very selfish request on my part. I hadn’t been able to traverse those stories of the heart. I’ve often been cast as the best friend or the gay assistant of whatever character got to explore those relationships. I said I’d rather play this guy, who seems to have a future of romantic triumphs and difficulties.

What will happen with Leonard’s marriage in Season 9?

I’m excited that Leonard and Penny have finally stopped talking about it and have taken the plunge, but that doesn’t solve any problems or answer any questions. So they’ll have a new world of loving struggle.

How is this third “Ring” installment different?

One interesting thing they needed to tackle is that nobody’s watching VHS tapes anymore. Now people can be cursed over their phones.