I have tried to explain to people how to use a nut and bolt to remove a pesky rotor and can never really explain it very well. Since I was doing just that tonight I decided to take some quick pics so people can see what I'm talking about.
Something to keep in mind if the rotor is really stick this is most likely going to chew it up. If that's the case it may not be reusable. Try this at your own risk.
What I basically do is take off the caliper and find any bolt a little smaller that the caliper mounting hole. I put the bolt in backwards with a nut on the inside of the mounting flange and thread it towards the caliper. If the nut isn't bigger than the caliper hole find a think washer that is bigger. Once the end of the bolt makes contact with the rotor tighten it just a bit, back it off, rotate the rotor a little bit and do it again until the rotor finally pops off.
Here is how I set it up.
This picture kinda sucks but you can see where the bolt pushes on the rotor.
If you look at the rotor in relation to the ABS ring you can see how much I pushed the rotor before rotating it and doing it again. After 3 or 4 tries the rotor popped right off.