As a fad, roller disco always bordered on the ludicrous. How do you glide forward on skates and get down with your bad self at the same time? Very awkwardly. Yet when you behold the teen boogie skaters of Roll Bounce, which is set in Chicago in 1978, those funky/silly movements give you a happy jolt of pleasure. It’s hard not to notice that the kitschiness of the dancing is what makes it so…optimistic. The director, Malcolm D. Lee (The Best Man), immerses us in the eager daze that ruled the final moment before the dawn of hip-hop. He knows how to use the great riffs of Chic and KC & the Sunshine Band to create a kind of Saturday afternoon fever, and he has a gift for coaxing nuance from the most modest of actors. Bow Wow plays the skate-dance hero in a way that’s never too cool to hide what an avid achiever the kid is, and he and his buddies converse in a fiendishly alert middle-class trash talk that keeps Roll Bounce jumping.