Besides the previous advice, try cutting throttle just before initiating those extreme maneuvers.
Big propellers at high rpm resist sudden nose up movements creating a force to the right.

Each snap roll needs:
1) Stalled wings (that is what your strong elevator input does)
2) Yaw around the CG (that is what the rudder does)

If you aren't feeding rudder, where the force that yaws the fuse to the right comes from?