Rodinal does not like A) high temperature and B) overdevelopment. I use Rodinal at 16 deg Celsius which requires to increase the dev time by a factor 1.6.
It is a good idea not to try receiving the box speed of the film because that leads mostly to overdevelopment.
With that in mind you can get a quite fine grain from Rodinal. Other devs can give slightly finder grain, but the grain itself is muddy.