After making sure everything is off, a good couple blows with a sledgehammer will get it off. That means new rotor if that was the plan anyway. Make sure the car is well supported if you are swinging under it towards the outside.

Put the lug bolts back in but thread them half way only. Get a piece of 2x4 about as long as the diameter of the rotor. Put the 2x4 centered across the bolts. Adjust the bolts as necessary so the wood sits flat on at least 3 bolts so it doesn't twist. Use 2 large C-clamps to pull the back of the rotor out against the wood. Tighten the C-clamps in unison so it pulls evenly. Good luck.

Take the rotor screw off. Put the wheel back on with the lug bolts finger tight. Put the X5 back on the ground. Back up or pull forward and then hammer the brakes. Rotor is now loose.

WOW, you guys are all GENIUS!!!!!!!!!! So many ways to break it loose. lol. Learned!!!

When dealing with large car parts which are "stuck together" you will be much more successful using a smaller force applied slowly (Clamps / pullers / levers) as opposed to a large forced applied rapidly (Hammer) to separate them.

Hammer is faster, closer, much louder, more manly man and lots more fun.

By the time you get it all clamped up I will have the calipers installed. My ears will still be ringing but it usually goes away.

I'm with redliner, BFH or bust.