This might be a little out in left field ( and I haven't tried a roller nut on a Les Paul ), but working both the nut slots and saddle grooves can really improve tuning issues.
What I like to do is make SURE the nut slots and saddle grooves have proper ramps and take-off points, aren't binding, pinching, touching the sides, etc. The ramps should match ( ideally ) or be steeper than the break angle of the string. I want the string to bend only once at the take-off point at each end of its speaking length, rather than have two bends close together.
Once the ramps are sorted out, I polish the insides of the slots and grooves with wet-dry paper using 800, 1000, 1200 & 2000 grit, and finish off the "face" of the nut and each saddle with a couple of swipes with 2000, in case there is a burr sticking out that might touch the string. Then a tiny dot of lube ( Vaseline, Chap-Stik, Nut Sauce, etc. )
If you can't do the work yourself with tools you already have there would be a cost either way. Personally I would avoid the roller nut, but that's just me.
Good luck with whatever you choose to do!