There are so many factors that go into this, its not just any one of them but the cumalative effect that causes the Corsair to roll better. Boosted controls or lack of them, horsepower/torque to weight ratio, length of the wings, wing area, negative static stability, size of control surfaces, servo trim, and many other factors, most of which have been mentioned already, all combine to make an airplane have good or bad rolling capability.
By the way, the Corsairs prop spins clockwise as viewed from the pilots seat, as do almost all US made aircraft. To the best of my knowledge the Zeros prop also spins clockwise, so that isnt why.
Also, somebody incorrectly stated above that most airplanes turn best to the right. Not true, most airplanes have props that turn clockwise as viewed from the rear, causing the airplane to want to turn counterclockwise, a rolling moment to the left. This means that most prop planes turn best to the left.
The factors that cause this are:
--P-factor (one prop blade creating more thrust than other due to angle of attack causing thrust axis to be displaced from relative wind)
--slipstream swirl (the corkscrewing motion imparted to air by the propeller which swirls around and causes horizontal lifting force on the vertical stab),
--torque
--gyroscopic precession (the force created when a force is applied to the rim of a spinning object, such as a propeller)
All these act to effect the ability of aircraft to turn in certain directions. On a normal prop aircraft, (clockwise prop) all of these except gyroscopic precession cause the airplane to roll and/or yaw to the left.
My guess is that the superiority of the Corsair over the Zero in this instance has far more to do with the control surfaces than it does with the engine torque. US aircraft in general had far more control authority at higher speeds than did Japanese aircraft of WW2.
