An aileron roll and a snap roll are two totally different things. Everything you pointed out in the video is an aileron roll.
A snap roll involves a rapid pitch-up and copious input of rudder to force one wing into a stall. The asymmetric lift quickens the roll (hence "snap roll" - it happens in a snap).
An aileron roll, despite the name, involves all three control axes (ailerons, elevator, and rudder) in order to keep the airplane traveling at a constant altitude and heading. Aileron rolls are easy to perform, but VERY hard to do as well as in that video.
That flip in the P-38, though cool, has nothing to do with snap rolls.
But those guys are great pilots, yes.
In fact, the best I've ever seen in Il-2, thanks for sharing!