[Mike Gerber]

That big nut does not have anything to do with the rotors. To remove the rotors you need to remove the caliper mounting brackets. If it's like most all Toyotas it should be 2 17MM bolts holding in on. Keep the brackets oriented to which side they came off of. They are different. Then if the rotor doesn't come off easily, screw 2 corresponding bolts in to the 2 threaded holes in the rotors. Tighten them evenly and the rotor should "pop" off. It is also a good idea to keep the rotors oriented to the sides they came off of so put some kind of marking on each one. I use white-out and put a "P" and a "D" for passenger and driver side on each one.

Mike