Pigeons roll and tumble because it is an instinct. Rollers roll and tumblers tumble because it is inbred and fun for them. My husband raised pigeons for decades. Ever once in a while he got a bird that wouldn't roll or tumble but this might have been because they weren't pure bred. On the other hand he got a few tumblers that tumbled right into the ground. You can't teach them to roll or tumble. They either do or they don't.