Though SXSW’s legendary music festival doesn’t start till tomorrow, bands the Roots and Band of Horses rocked the SXSW film festival, which kicked off over the weekend. The bands played the Samsung Galaxy Sound Stage Series after a premiere of the Paul Rudd film “Prince Avalanche.” Also at the film’s debut in Austin were Joseph Gordon-Levitt and “Girls” star Alex Karpovsky. SXSW’s film and interactive sections drew Jim Carrey, Steve Carell, Olivia Wilde, Chuck Lorre, Al Gore, Tesla Motors man Elon Musk, Danny Boyle, Robert Rodriguez, Richard Linklater, Adam Brody, Sarah Silverman, Michael Cera and “The Avengers” director Joss Whedon, who debuted his black-and-white Shakespeare project “Much Ado About Nothing.”