How do I get the rear rotors off

Get your self a 3 - Ib or 4 - Ib steel sledgehammer with a 10 inch or 15 inch long handle whatever you feel comfortable with and give the rotor a few good whacks in between the studs that will get it off. Be careful if you do not do this all the time you may hit one of the studs with the hammer and mess the trends up on the stud so put lug nuts back on enough so if you make a mistake the hammer will hit the lug nut and loose enough so that the rotor can pop off when hit with the sledgehammer. Sometimes they can be pretty stubborn to come off but a few good whacks should do it.

Would not hurt to spray some WD40 on and around the center of the hub where rotor sets.