EDIT:
More testing...
My conclusions:
MB roll is terrible against his straight shot. Not only is it hard to get through it but even if you do you don't get a punish and at some ranges he even recovers before you. Meaning you spent a meter to let him pressure you.
MB roll is USELESS against his MB rifle. If you don't get hit at the start you'll either get hit at the end or even if you can block at the end of the roll you still get pushed back out of range.
MB roll is decent against his trick shot. Its still can be hard to time it but if you do he recovers fairly slow so you can defiantly punish(the vid doesn't show this clearly but you defiantly can punish the recovery on this if you make it through).