Have you removed the two large phillips head screws? That is the only thing that holds them on when the wheel is off. If the rotors have seized to the hub, one trick you can do is pull the wheel, remove the phillips head screws (2) and then put the wheel back on but with the lug nuts just finger tight. Lower the car and slowly move it a few feet and apply the brakes hard. Without the wheel tight against the rotor, the rotor will shift on the hub and free itself. Jack the car back up, pull the wheel, and the rotor should be loose.
The only other alternatives are to hit the outer edge of the rotor with a brass hammer. Or, if you are planning to replace the rotors, tap, and I do mean TAP, the edge of the rotor with an 8lb sledge hammer. DO NOT POUND IT, YOU WILL DAMAGE THE WHEEL BEARINGS! By just tapping, the mass of the 8lb sledge hammer will jar the rotor enough to break it loose. I had to do this on my 2002 to pull the rotors for trueing.