In the movie the OP is using ailerons so he's not actually doing snap rolls. A snap roll is just a horizontal spin, entered at a slower speed by grabbing full elevator while kicking full rudder snapping the rudder-side wing into a stall (I usually jam on the juice at the same time for more control authority - it MUST RASPECT THA AUTHORITEH).

I don't have CoD so I can't comment on it, but 1946 didn't model initial roll rate, all aircraft reach their maximum roll rate in the same amount of time (something like 1/2 second - I haven't timed it). So a P-47 with no ammo or ordinance reaches its max roll no quicker than a P-47 with ammo and a pair of 500 pounders. In the stalls the CG feels like it backs up about six feet -lol- no further comment.