Thanks for all the suggestions. Turns out that I don't have access to a torch (although I'm beginning to think they are handy to have around), and it also turns out that I was using the wrong tool. My dad had an old 2.5 lb sledge, and a few whacks from the backside took the rotors right off. My jaw just about fell to the floor when I saw that happen.

Lesson for the day: when dealing with old rusted rotors, use a sledgehammer.