Oh, Goddess Shinki. Ummmmm... Hard to say. The Doujin music is a HUGE part of my love for Touhou. Probably the biggest. As far as rock goes, I'd say:
-Pizuya's Cell
-Foreground Eclipse (More Metal than rock)
-Draw the Emotional
-=NeutraL=
-Crow's Claw
-Buta-Otome
-Shinigiwa Satellite
Some may not be strictly rock, or more on the Metal side of things... or not entirely rock at all. I'm not a musical expert ;^^ To be honest, the ones I mentioned are already fairly popular. Shinigiwa Satellite and Draw the Emotional are two that I feel are REALLY good, but just don't get that much attention. If I had to pick 3 of the ones I listed, I'd go with Pizuya's Cell, Draw the Emotional and Shinigiwa Satellite. Foreground Eclipse is more metal than rock, but that's probably my favourite circle from what I listed...