If you have OE shocks, for sure they have been shot for quite a while. That is what would cause the rocking motion. Unfortunately due to the stiff springs etc on these trucks the bounce test of pushing the bumper up and down does not work, but just the fact that you are getting that rocking motion tells me the shocks are gone.
As far as the brake rotor is concerned, make sure that the lug nuts are torqued to the proper number, 150 ft lbs. Uneven torque on the lug nuts is the main reason for the rotor to warp.