My kids do forward rolls. They are a progression for forwards inversion on beam. You would be surprised at how many kids are scared to even do a pike stand and tip over forwards - yet they are expected to do a vertical handstand on beam.
Then they progress to handstand hold forward roll. We generally use pads on the beam.
Also, despite the replies in this thread, this is not uncommon at all. This is addressed in the level 3/4 compulsory beam drills at every USAG Congress and is part of Tom Koll's drills for the compulsory routines.
Backwards roll is more uncommon because you either have to a back shoulder roll (eh, not really the same) or something that is probably harder than a back tuck.