As Jimmy Fallon's house band, the Roots appear on every episode of Late Night. But last night was a bit different, with the group stepping up as the featured musical guest to perform "Tip the Scale," a cut from their new concept album, undun. They weren't alone. In addition to the regular band and emcee Black Thought, the song was filled out with guest spots from Bilal, D.D. Jackson and the Metropolis Ensemble.