Okie here we go:
5 letters, so that at least two are between two Rs.
So we have:
where X can be any letter of the alphabet (assuming, including R!)
That's really going into the problem "Jamacian me Crazy!"
Looks like Apollo nailed it.
R is the same letter, so we can only shift it in three possible ways to leave at least a gap of two spaces in between.
As for the other three letters, the stem didn't specify that they had to be English