well you cant do a rolling harrier anywhere near right and not close to perfect without rudder .. the rudder is needed along with slight taps on the throttle to keep the nose in the air.. rolling circles can be done without rudder because the plane is remaining straight you have one elevator movement down, one for the turn and one up.. BUT if you get in a habbit of using your rudder it will be alot smoother and to me i feel like i got more control over the motions even if the rudder input is ever so slight..