I think the scrapes will completely disappear, just like if you were to scrape yourself some other way. I know how scary it is to see many of them at once, making it look worse than it is though. I think you'll be fine. I completely understand you not wanting that to happen again though, and sorry that happened.
I have never used a derma stamp myself, so I can't speak for that. I have only used regular rollers. I recently ordered a couple 3 line rollers, but have not received yet. I wonder if the three line would work well on stretch marks and hopefully not have the problem with the plastic on either side scraping or touching? I am only wondering out loud, as I have no idea myself.
I will be interested to read what Sarah has to say on this issue. I would not worry about the scratches though. My very first time to roll (which was my legs), not only did I use a cheapy roller (not purchased here), but I went back and forth without picking the roller up each time, and I did that "star" method really fast. My legs were covered in track marks AND scratches, because since I was doing the star method too fast, I was getting scratches probably similar to what you have. It took a few days for the track marks to disappear, and longer for the scratches. They did all completely disappear though eventually, with no marks at all. Don't worry.