I don't really read the comics, so what does Robin DO besides "be Batman's sidekick"? I know he's supposed to be a great acrobat. Maybe swordsage?
No ToB, or I'd say Unarmed Swordsage as well.
Robin (well, Dick Grayson, at least), was an accomplished acrobat and performer. Bard would be good, but I'm thinking a bit differently, possibly a Combat Maneuver specialist. He does a LOT of tripping and throwing in the comics. If this were PF, I'd actually suggest a Maneuver Master Monk. If ToB were allowed, an Unarmed Swordsage focusing on Tiger Claw and Setting Sun maneuvers.