If you need opposite rudder to keep the nose up, you are overbanked for the turn radius, in other words you are doing sort of a knife edge turn.
The ailerons and rudder don't exactly get used together. Once the ailerons have established a desired bank angle, they need to go back to neutral or else the plane will keep rolling, however, the rudder along with the elevator still get used to carve a coordinated turn. When a plane is in a 45 degree bank, the elevator and rudder act like the two halves of a V-tail elevator and together swing the plane's tail around to make the plane turn. Generally, the less the bank angle, the more the rudder does and the less the elevator does.