ironstream: lol you caught it and mentioned it before I did.
yeah, setting the pitch, angle, and roll back to zero after the rotation is called would be best. I don't think there is anything else to remedy the problem while keeping the code you have there.
even if you check for a pressed key before checking which key is pressed wouldn't remove the rotation problem. It would mean, if any key is pressed, regardless if it is the one's you've chosen, the ship would rotate since the values aren't returned to zero.
-- from my island, aloha wau 'ia 'oe --