You might want to ask this in the beginners forum but I will attempt to explain it to you here.

1. Enter upright at 200 ft.
2. Attain proper airspeed
3. Pitch the nose up 5-15 degrees.
4. Apply left or right aileron
5. Allow the plane to rotate along its axis 1 full turn
6. Exit upright

The plane you are flying should not require rudder to do a basic quick aileron roll. If it does you have your rates too low. It may however require you to add a little forward stick during the inverted part of the roll.

The only time I use rudder in the roll is when I am doing a harrier rolling sequence or Harrier rolling circle or doing one super slow long axial roll the length of the field. Rolling harriers require deep precise rudder inputs and the long slow axial roll requires a transitional sequence between the aileron, rudder and elevator.

I have told you far more than you need to know about rolls I feel comfy in saying that your problem is that you may need to increase your throwage for your ailerons and feed in some forward stick on the inverted half of the roll.