As I understand it, grain size does not increase with Rodinal... It stays the same. Rodinal works very cleanly, and it leaves the grain sharply defined, in place of "smearing" the edges to give the illusion of fine grain.
It is a high acutance developer, producing sharply defined edges, without grain "clumping".

I don't consider "grain" to be any sort of an "evil" anyway. Robert Farber made some wonderful images using grain as an aesthetic "tool" - Agfachrome 1000 reversal film pushed as many as two stops in developing.