I'm thinking Red John is Walter Mashburn. He and Patrick became friends rather easily. I'm not sure where the name "Roy" fits in with Mashburn, but it doesn't seem to fit with any of the other leading suspects. Mashburn definitely has the resources necessary to be RJ. And here's another reason:
From Redline(2010)--
Teresa Lisbon: We get it. You're an energetic man. You like danger. So why bring us here?
Walter Mashburn: I have no love for danger. Nothing's dangerous if you think ahead. If you plan it right, you can get away with... well I was gonna say you can get away with murder, but you know what I mean.
Walter Mashburn: Oh, I know you're a charlatan as I said. You lost your wife and kid to a serial killer, your fault you think. And now you're on this hopeless quest for redemption. Battling evil and injustice, right?
Patrick Jane: Close enough.
Walter Mashburn: You play mind games with people. You size up their weaknesses and then you give them the rope to hang themselves.
Patrick Jane: Oh, you make it sound so cool.
Walter Mashburn: So it's over?
Patrick Jane: Yeah. It's over.
Walter Mashburn: That's too bad. It was fun.
Patrick Jane: Yeah. How you gonna top that thrill?
Walter Mashburn: Maybe next time, I'll be the killer.
