I've made a few rods over the years. There is no "best" rpm for lathes. It really depends on the wood (type, thickness,etc..) the tools used, your comfort level with the tool, type of finish, etc... You want to make sure you don't create an accident by going too fast (this is more dangerous than going to slow) Start at 600rpm and speed up a little at a time until you reach the best speed for safety while still being able to get the project done in a timely manner.

I'll give you a link to a site specifically for custom rod builders that has alot of good info.
http://www.rodguild.com/