Here is a technique that I've seen work on a bolt with a stripped head: use an epoxy to glue the tool to the fastener. You will need to use a screw driver that you don't mind throwing away and some JB Weld (or some other metal epoxy that will set really fast and the faster the better...I believe I have seen a product specifically designed for the purpose of removing fasteners with stripped heads...you might ask at your auto parts store). Use masking tape around the screw head to keep the epoxy from getting on the rotor ( you wouldn't want to make things worse by glueing the screw to the rotor) and then glue the screwdriver to the screw. Hold it till it sets and then let cure for the recommended time. Then try to remove the screw.

Good luck...