I have built several different style roller rockers for myself over my years of racing. I would be happy to assist you in setting up and machining them.
Your thought about holding them with down with pins and bosses is right on. Make a fixturing plate with a dowel pin going thru the hole where the roller pin goes and then make another tapped pin where the roller brg. or shaft will go. A simple thick washer and grade 8 socket head capp screw will hold them in place for profiling. The selection of material is EXTREMELY important so as to not have the rocker fail from fatigue and stress. Also oiling of the rocker roller and trunion is critical to life support for your engine. If you have furthur questions contact me at: [EMAIL="email@example.com"]