Hi Crystal,
We are so far the only vendor that offers a single needle, so there wasn't any data on its use. We tried to recommend a schedule that we thought would be close to optimal, based on what we understand about skin regeneration.
The reasons for recommending to use the dermaroller first is mainly that it stimulates the surrounding skin as well. Many things happen when you roll skin. You'll increase the bloodflow for quite a while (days), which increases oxygen levels, temperature and triggers certain very complex inflammatory responses that initiate skin regeneration. These processes are incredibly complex and one can drown in the details, explained in countless thick research papers. If you'd just single-needle the stretchmark alone, we thought that might be sub-optimal. However, we can't be sure of that. Nobody can really say they know. We know that the single needle works because we have customer pictures to prove it and the clinical data exists to back it up (that on scars and stretchmarks with hardened collagen, localized, exactly targeted longer needles work better than 1.5 mm needles or even 2 mm needles, due to selective crushing of scar tissue).
We had one more reason for advising to use a roller first: Contrast optimization of the scar. We thought that if you would single-needle the scar only, without rolling, that there would still be a spurious boundary between the normal skin and the stretchmark. We thought that rolling first would help "blur" the stretchmark with the surrounding skin, by initiating an inflammatory reaction in both, triggering new collagen and elastin in both, creating a smoother transition between normal skin and stretchmark. We know someone who got good results by first using a very strong abrasive on the surrounding skin and then using a single-needle technique similar to ours. Using a dermaroller instead of an abrasive should be safer and give an even better result (because it goes deeper).
So this is based on educated guesses, basically. You are free to think about this yourself and decide how you'd like to approach it. It depends also on how wide your scars / stretchmarks are, and how big the contrast with the surrounding skin is. So you are free to experiment - what we gave is just an educated guess. One year from now we'll be in a better position to make more definite statements.
Hope this helps :-)