Do you really need to roll for like 10-20 minutes? Study was 20 minutes if I remember, but that seems awfully long. Wouldn't it just take like 2-3 minutes to do the whole scalp?
Doesn't seem long to me. I only use the derma roller on the frontal region of my scalp and that already takes 7-8 minutes if done thoroughly and in all directions. If I had to do the entire scalp I'd definitely invest in one of those pens I guess.
Also, remember that you only do it once a week. I think 20-30 min a week really isn't a lot of time.