Here are a few theories on Robert Kirkland. I don't think that he is RJ, and I think that him getting a facelift is absurd. I hope that the writers wouldn't do that to us the viewers. But I do think that he is corrupt in some way. 

1. He is an accomplice of RJ. Probably very high up, but rarely seen because of his deep cover in Homeland Security. He may be RJs right hand man, even. He was seen by Jason Lennon once many years ago, and RK asked Jason if he could recognize him. Not because he has a "new face", but because he could have blown his cover and wants to be sure that no one else knows who he is. If Lennon had known who he was, RK would have had to kill the people he had told about RKs true identity. He kills him anyway because he is ordered to do so by RJ, so that Lennon can't tell Jane who Red John is.

or

2. Robert Kirkland is/was involved in the operation going on at the shelter and bought one of the women that were being sold. That would also explain him wanting to know if Lennon could ID him and thus know if he had told anyone about RKs corruption. RK then killed him so that he wouldn't tell PJ or anyone else about his involvement in the operation at the shelter.

or 

3. Both. RK is Red John's right hand man, but was never seen by Lennon until he bought one of the women from the shelter. Not knowing that Lennon worked for RJ at the time, he didn't use a disguise. So RK had to make sure that Lennon didn't recognize him so that he didn't tell anyone (especially RJ) about his involvement with the shelter. This would both cost him is job (and cover) in Homeland Security and probably his life from RJ for making mistakes.

Those are my theories on RKs involvement. Hope you like it!