I replaced my brakes last year with slotted / drilled rotors. I think I need new brakes now but I was curious as to if I should replace the rotors and pads or just the pads. I don't see or feel any grooves in the rotors. What do people typically do when it comes time to replace drilled rotors?

I think you will have a hard time finding a brake shop that will turn slotted/drilled rotors. Use a dial caliper or a micrometer to check rotor thickness in a few areas on each and see if you get any great variances in thickness. If you suspect any glazing, you can use some fine grit sandpaper with a orbital sander to knock the glazing off.