Well... you say this problem cropped up after you installed new rotors and pads, right? When you replaced the rotors and pads did you remove the rubber bellows from the caliper bores and inspect/clean the exposed part of the pistons before pushing them back into the calipers to make room for the new pads? If not, then odds are pretty good you could have sticky calipers!

The pads take years to wear so a band of crud can develop around the exposed part of the piston. The boot provides good protection from stream fording, pressure washing, salt spray, etc. but it's not 100% leak proof. If in the process of installing fat new pads, you just shove that crudded up part of the piston back into the bore, you run the risk of dragging brakes. (and possibly ruined seal too although it is set back into the bore far enough to avoid that in most cases) Best to take the time to remove the boots and inspect the pistons. If dirty, clean the piston with a brass brush or some brass wool or fine steel wool and rubber friendly solvent (brake fluid works well) hose it off with perc then blow it off with air - especially if you used steel wool. Now you can push the part of the piston that has been exposed for several years back into the bore without fear of it sticking.

Or hey - maybe the new rotors and pads are just a tad thicker than OEM and the tolerances stacked up and you're getting brake drag from that...