Any special precautions when mounting to edpm roof?

Well nuts do indeed create a water tight seal, provided you also slather up the screw itself. The EDPM roof bunches a little as the rubber of the wellnut compresses and deforms (as it should). I didn't have any problem with the EDPM roofing twisting along with the drill bit. Just cleanly sliced right through it. I used a 1/2 wood bit at high speed. No worries, easy peasy.