I have noticed a scene and I wanted to share it with you guys.. check out the 8th episode of the 4th season starting at 25:00.. it puts Ron right in the center of the spot, and it distinguish him from all surrounding agents
Peace!

For me, CBI Ron is red john or his right hand man
cmonn guys, he is always in the background his real name is John Troy Donovan!!!!
many scenes in the series made him guilty, the first time he was seen in the series was in "seeing red"!! , he doesn't speak alot, he wears the same ring as red john, he has been seen walking with many red john disciples, heez got the body for it, when he appears, the red john weird sound go on. If he is not red john, then iam 90% sure he is his right hand man.

an interview between Owain Yeoman (Rigsby) and John Troy Donovan (Ron), at this link

http://www.youtube.com/watch?v=0llrwyH08Sg&NR=1&feature=endscreen

 from that link, Owain asks John directly if his character, Ron, is in fact Red John.  Donovan responds by saying, "I can't say...but I think you know, don't you."  To which Owain replies, "Yes, I think we all know."

Hello lads, I am Red John :) You will see.

Kirkland is a decoy IMO, he'd be far too obvious to be RJ. He strikes me as someone out for Justice, much like PJ. 

I'm thinking it could be CBI Ron, or he could be an accomplice. He works for the CBI, and we've long suspected that RJ has an insider at the CBI, or works for the CBI himself, given how he's able to access their servers and even access the building himself (like when Rebecca was murdered in season 2). Also, the old saying is "keep your friends close, but your enemies closer". How better to analyse and watch Patrick, than to spend each day in the same building? 

For all we know, the list given in season 5 could be a decoy, Bruno may have said that the list was real, but he's backtracked on things before, and this could be another bluff.

To end, in season 4, when RJ's at Rosalind's house, we see RJ's arm holding a teacup, and he's wearing a suit much like Ron wears, is a similar build to Ron (in arm thickness) and has a hairy hand, Ron is hairy.

Going on the theory that Red John is someone we saw in the first few seasons, and the writers hinted that he was hiding in plain sight, then it makes sense that CBI Ron is Red John. For starters, he's about the same size as RJ, he has insider info on the cases, and could have used his position to get to people like Rebecca, Renfrew and Wainright. Plus he's unassuming, he could looks like he could easily hide the fact that he's a mass-murdering sociopath.

We have to all agree that CBI Ron is not Red John but is definitely working with Red John.....He is Red John's mole in the CBI....

Because it comes to question, why is there a recurring character or extra in more than 75% of the scenes, unless he has a bigger role which is to be revealed when the show nearly finishes.....