hmm....I don't recall finding a 32mm nut on my rear brakes when I replaced the pads and rotors. remove the two (I believe they are 17 mm) bolts holding the caliper onto the rotor, slip the caliper off (have something nearby to rest the caliper on so lines aren't damaged), take your e-brake off so you don't fail like I did and wonder why the hell the rotor won't come off, pull the rotor off. If it gets stuck, whack it with a deadblow or something. Although, they do also have threaded holes in the rear rotors for a tool that screws in and pushes the rotor off the hub assembly. You can also use properly sized bolts/screws. But, with the e-brake off it shouldn't be a problem.
Edit: Come to think of it, 32 mm is a pretty big nut. Good chance that's the nut on the hub assembly, which you shouldn't have to mess with for brakes. If you were replacing the rear axle shaft maybe, but not for this.