It's not just a function of aileron effectiveness - it's a function also of the roll/yaw inertia coupling on a given aircraft, the amount of sideslip that may build as beta and alpha are exchanged, the degree to which, say, fin strength margins are in excess of the average, and many other factors.
The amount of time you extend the roll also matters - again, it gives longer for the sideslip to build. The Hawk, IIRC, has a whole family of limitations as a function of total bank rolled and stores configuration - some are quite restrictive.