I know rolling under recoil as the old cannons that were allowed to role back a bit when fired . Free recoil in shooting is allowing the rifle to slide back under recoil, a lot of BR shooters shoot this way, line up the shot and the only thing touching the rifle is their trigger finger , you tube would give good examples of this .
I can't say I've ever heard of rolling under recoil in terms of shooting a rifle . Sorry!
Shibby , what your referring to would just generally be called torque twist I suppose , But I can't say ever notice my rifles twisting when fired .. It may be more of a technique "issue". If its effecting your accuracy