I think they are still an elite form of officers. Ordinary ground duties are - as I see it depicted in the series' - done by ordinary Starfleet personnel, the RRTs are fast response units, who are deployed in case of emergencies - in POF there is a ship mentioned, I tihnk it is Bolarus-Class, an escort which is intended as especially used for RRTs for deployment. They are trained in small unit tactics, infiltration, etc. But I think they are also used as boarding units, etc.
However if I remember correctly there is an archetype of RRT-officer in the back of the Player's guide, which might explain some more.
We came in peace, for all mankind - Apollo 11