This is strongly suggested:
1. Clean the hub face with a wire brush and brake cleaner to the new rotors are sit parallel to the hub with no chunkies in between.
2. Clean the threads of the lug studs in the same manner.
3. Put a light coat of light oil on the hub face and threads (just a mist) to repel water and lightly lubricate the threads for even wheel lug torque.
4. When you torque the lugs, pre-torque them all in a staggered pattern to 50 ft/lbs, then 75, then 100.
When you don't warp your front rotors, this little extra work will be worth it. Our cars from from the factory are a little under-braked. The rotors are prone to warping, and a good number of us have. If you ever have your wheels removed and reinstalled by a shop for any reason, go home and re-torque them.