The reason i never liked the dermarollers was the needles never seemed to go all the way into the skin - you need to actively watch the pressure you're using on the roller. That's why fewer needles are better - it's easier to "jab" it into the skin. You can get a good angle on the roller while you're rolling to see if the needles are penetrating. Dermarolling should hurt when done properly. The skin is often bloody, rough, and swollen when complete (at 1.5mm+). If your face is red or swollen, I'd leave it alone before reattempting.