You get a heavy weight like exercise hand dumbbells (about 5 lbs) and a length (maybe 6 ft) of strong narrow rope (like a 1/4 inch).

Tie the rope in a loop (so you'll be doubling the strength of the rope), and then twist the rope in a figure eight pattern around the both arms of the rotor (so that the rope can pull up on the rotor evenly). Loop the opposite end of the rope around the hand weight.

Now, there should be enough slack in the rope to swing the weight in a long upward arc. When the weight rises to the top of the arc, the doubled rope should go taught, and the inertia of the fast moving weight should produce enough sudden force to break the rotor loose; and yet you're not using any prying tools that could break the rotor.

I've often had to use this method when I first do a tuneup on a car that I've bought -- I've always had the bad luck that prior owners of cars I buy never seem to use antiseize on the rotor. I do, and I never have a problem for subsequent tuneups.

Use a dollup of antiseize, next time.