Let's first admit that there's not enough information too be sure of our choice.
My suspect is Ray Haffmer, he's the only one left after a process of deduction.

I started with the description of Rosalind. I do not count height because they are all very close together and I don't think a blind woman (or anyone without a measuring tape) can be precise to the inch.
Rosalind's description removed Bertram, McAllister and Stiles from my list.
Bertram is obviously bold, and too heavy to be RJ. Even if Rosalind's information is incorrect, he doesn't match the body type of RJ. (We must not forget that we have seen him when he rescued Jane from his copycats)
McAllister is too old to be RJ, his skin texture differs too much to go unnoticed by Rosalind. He is also too creepy and awkward for RJ. RJ is charismatic, intelligent and a charmer, otherwise he would never have managed to create such a loyal groups of followers. He might try to hide these things to protect himself, but his narcissistic nature won't allow him to play a fool.
Stiles is also too old and probably doesn't have strong hands. Stiles is into manipulation and is at the top of an cult. He doesn't do physical chores, so his hands are probably very soft. He does enjoy to play games with people, and thus enjoys to play mind games with an intelligent man like Jane. This is very like RJ, but Stiles methods are different. RJ likes to play games and teach his component that he (RJ) is always smarter, always one step ahead. Stiles games are puzzles that Jane can solve, and Jane (almost) always profits from the outcome of the riddles. Stiles is however involved in everything, I think he is pretty conflicted. On one hand he wants to help Jane, but on the other hand he protects RJ.

What really bothers me is the popular thought that Partridge is RJ. I can't understand that one.
It is shown that RJ gets very angry when his work is copied. He can't help himself once that happens, he has to harm or kill that person. Otherwise he would never have killed Panzer 'for' Jane, since RJ likes to be in charge. The first time (I think it was) we meet Partridge is when he shows Jane and the team around on a fake RJ case. He is in his element, very theatrical. This seems like RJ, because RJ likes dramatics (playing with emotions with his smiley face). But RJ wouldn't be able to be this way when he is talking about a (very bad) copy cat job.
An other point is his behaviour in general, he seems a bit foolish and Jane talks down to him without any payback. Remember that that is exactly what caused the death of Jane's wife and daughter. RJ hates it when people make him feel small or stupid and goes to great lengths to prove he is the smartest man alive.
His body type matches pretty good, he doesn't look bulky or very soft. He probably isn't strong enough to take people down hence the taser.
But I don't think the taser is a sign of a weak body. It is very effective and clean, and that's why RJ uses it. RJ works very precise, sees his kills as a work of art. With a taser he can avoid a struggle and minimize the risk of leaving evidence.

I had to look up Reede Smith, because I didn't know who he was. Purely looking at his character, there isn't much to say. Only that he is too broad to fit the body type (at least, it seems so in the picture). Of course his name is perfect, but it is too obvious.
When you look at the build up, it would be weird that RJ gets introduced in the 5th season and only gets one episode. I cancel him from my list based on this fact, it's very feeble and I am aware of that. It is mentioned that we would be dissapointed to see who RJ is and that would certainly be the case with Smith. But I don't think that is enough to make him RJ.

Then it's down to my two 'favorites'. 
Kirkland seems to fit the part, with him killing the guy in the hospital and stealing from Jane. That however, is exactly why I decided it isn't him. I have to admit, it is only because of the way the series is filmed, so I won't be surprised if I am wrong about this.
Kirkland lacks the subtle, almost elegant vibe that RJ has. He is very 'solid', while RJ is as solid as thin air. RJ is able to go everywhere without getting noticed, there is always that sense of mystery.
He is however cold as ice and a good lair. He would be an excellent accomplish of RJ.

Then we have Haffner lets start with his career.
He worked at the FBI as an expert in wiretaps and creative surveillance techniques. Wouldn't that be handy for connections and skills. It would certainly explain how RJ is always a step ahead (because even a good spy wouldn't be able to get into Jane's room to view the suspects).
Then he came to the CBI, he shook hands with Jane and it is clear that Jane doesn't like Haffner.
Haffner is a member of Visualize and has learned to profit from is charismatic and charming manners. He also has the right age to be at the farm.
When Jane was on his team, he tried to control him by being smarter, which failed. RJ is very intelligent, but is used to the advantage that he knows and sees his component while Jane is fighting an invisible force. So it is very plausible that RJ can't compete with Jane when he is out in the open and isn't surrounded by people who are his puppets. RJ needs his followers to cover up mistakes (to kill witnesses etc).
A few fun things about Haffner, his name Ray comes incredibly close to Roy (the name Rosalind uses for RJ) and it is kind of a mindf*ck that Haffner and Jane were in the same team for a short time.
There are a lot of things that I have forgotten to write down, but my fingers and brain hurts from typing this. I apologize for mistakes, English isn't my first language.