For me RJ is Gale Bertram. In the last episode of season 2 RJ mention to Jane a poem of William blake called "Tyger" that begin like that : "Tyger! Tyger! burning bright...In the forest of the NIGHT..."
The first appareance of Bertram is in the first episode of season 3 (red sky at NIGHT) and Jane answer to Bertram what he do on the crime scene. 
Bertram is the one that knows all the poems of William Blake (Tyger too) and was on the one suspected the crime scene when Partrige was killed. 
So : Bertram = RJ