If all you are doing is installaing rotors, that's it, then figure a shop labor charge for about an hour of work. The place I use to work at would have charged you about $70 labor for that hour. Installing rotors isn't rocket science at all. Basically, remove your wheel, unbolt the caliper (2 bolts), unbolt the caliper bracket (2 bolts), then remove the rotor by hand or with some guidance from your favorite ball peen hammer. Slap the new rotor on, put your bracket back on, lube your caliper slide points and the backside of the pads, install caliper, install wheel. All done. Simple hand tools, a floor jack, and some jackstands is all you need.

I'd look at buying the rotors yourself and then spending the hour or so out in the driveway on a nice weekend afternoon getting it all done yourself. It's not difficult at all, it's not terribly time consuming even if it would be your first time doing it, and you also get the satisfaction of doing it yourself while learning about your truck.

Just my .02...