I doubt a warped rotor is going to cause the entire assembly to vibrate like mad when he's not using the brakes. It's also not going to suddenly come and go like his problems seems to be doing.
I would guess maybe strut mounts, the steering stabilizer or even ball joints. Any chances a CV is binding up causing this?
I'd definitely look at the entire front of the of truck (balljoints, tierods, CV's, etc) and see what's going on.