Lack of results on forehead after, what to do?

[Planning]

Hi, I've gotten some hair back since I started dermarolling in august 2019, but foremost on my left forehead I've barely recovered anything.

I use Minoxil twice a day, also a 1,5 mm dermaroller once a week for 13-15 minutes. What should I do to get my hair back on my forehead? For example, should I try a dermapen instead of a dermaroller?

Thanks in advance for replies.