There is absolutely no evidence to support this theory that Sheriff McAllister is RJ, just going on the fact that Xander Berkeley is not the sort of actor you bring in for 1 episode, in such a small role, and then never see again. That's how thin this theory is.

He doesn't fit the physical description, he wouldn't be able to gain access to the CBI, he doesn't look like the Visualize type, and he's probably too old. But again, why cast a good actor in such a small role, and why is he on Jane's list? 

My theory is that RJ is older than people suspect him to be. Haffner (if my maths is correct) is 46 years old, Bertram would appear to be about the same age, Partridge is dead, Kirkland looks in his late 30's, Smith looks too young, and Stiles is too old. 

Which leaves McAllister, who is based in Napa county (which O'Laughlin mentioned before), roughly mid 50's (right age for a serial killer, would have been about 40 when he started). 

In RJ's friends, the writing "he is mar" is seen on the wall. As the hooker was mexican, maybe she misspelled McAllister "Marcallister" ( i did say this was thin).

And finally, maybe he changed his appearance to fool everyone? Xander Berkeley cleans up pretty well for a man his age, maybe McAllister is the same.