A faster servo will not make your plane roll faster.

What you need it more control throw. That means moving the pushrod out on the servo arm (or installed a longer arm) and/or moving the pushrod in on the control surface, or installed a shorter control arm.

You might need more torque on the servos, since as you increase throw, you decrease the mechanical advantage of the servo.

An easier mod to do before replacing the ailerons is to use dual aileron servos. Cut the torque rods off where they exit the aileron, since they sometimes limit available throw. Now mount servos half way out on the wing driving the ailerons directly.

However, there is a point where you''re just asking too much.

Oh, and making longer ailerons won''t really change the airfoil in any important way. It is a viable way to increase roll rate, but it also makes it easier to get aileron flutter. A single servo moving the aileron at it''s root means the entire length of the aileron is free to flex. A servo driving the aileron at the center means the aileron flexes less and you get more effective throw at the tips. And it''s at the tips that you get the most effect from the ailerons.

Also, try moving the CG back. that will really help your elevator AND it will help the roll rate, and make the rolls smoother as the nose will drop less when inverted.