My opinion on this: rolls should be possible for eveyrone in light or medium armor even if bumped, even if dehoresed - BUT - rolls should NOT BE POSSIBLE for guys in heavy armor (at least much slower and not so far).
Rolling in full plate armor is utter bullshit im my blind eyes.
EDIT:
maybe even tie it to agility somehow or make an atheltic skill for rolling, jumping, kicking, nudging, s-keying and all the other fancy moves no one likes.