Sara Gilbert, best known for her role as the wise-cracking daughter Darlene on "Roseanne," has joined the cast of the 20th Century Fox feature "Light It Up," Reuters reports. The film, which also stars Forest Whitaker and Vanessa Williams, is about a group of students who take over a run-down high school in an effort to improve it. Gilbert is also developing two television series. One, "Even the Losers," which she created and will direct for MTV, has been picked up by ABC. It's described as an edgy high school series about a 15-year-old Woody Allen-type who is shipped off to boarding school. Additionally, she has a CBS deal to develop and star in an as yet unnamed comedy series.