Hmm, let's see...Everything was OK until you had them rotated and then it all went in the dumper (so to speak). Make sure the direction of rotation was not reversed on any of the tires in the process of rotation. I'd have the dealer put them back the way they were originally and start over again. The owner's manual gives the correct rotation sequence. Make sure they follow it. If your mech states warped rotors cause tire bounce at highway speeds, then he doesn't know what he's talking about unless he drives with one foot on the brakes and one foot on the gas (at highway speeds...did he really listen to what you were telling him??) What you are probably dealing with is harmonic standing waves in a tire rotating the opposite direction it was designed to rotate in. Just spinning the tire will not reproduce the problem. There has to be contact with the road to produce distortion of the casing..yada yada yada...Put 'em back to their original locations and see if the problem goes away.
