My personal experience and from observing the results of other forum members...
Most users who reported any gain from dermarolling/stamping were also on Finasteride/Minoxidil.
Those who reported a visible impact have noticed thickening of the vellus hair, which only grow to a certain length before they stop growing any further. While this may not take you down one Norwood scale fully, the gain could be visible enough to make some people content (especially if you are into buzz cuts).
My experience is similar. The vellus hair never became properly terminal, but it has made me look less of a shiny baldy, more of a guy with very thin hair and a big forehead. I personally don't feel that it is enough and would like a hair transplant.