What 15" aluminum wheels are you guys running over the 11.75" rotors?

The issue with factory Jeep aluminum wheels is twofold:
The deep backspace (4.5" if I remember correctly) on 15x8s hit the rear springs if in the stock location, as you said, you'll need wheel spacers. If you've got a spring relocation kit on the car, you may be good. The 15x7s MAY clear, but I can't verify at the moment.
On the front, the centerbore doesn't clear the hub- it tapers down as it nears the outside of the wheel and doesn't allow the wheel to fully seat against the rotor face. You need to have the wheel bored all the way through.
Longer studs may also be needed.