Roy Carmen first appears in The Scarlet Letter. He's a psychiatrist, therapist of CBI, who Teresa Lisbon is forced to see after an officer-involved shooting. She tries to avoid him but he just pushes more until she talks. She wonders why she is the only one he is pursuing and not Jane since he shot Dumar Tanner. He reveals that after five minutes with him he seemed normal. Lisbon eventually opens up to him and they meet daily.
When Roy reappears in the next episode, Red Badge, he and Lisbon have a cup of tea and she leaves. The next day a pedophile by the name of William McTier is murdered and everyone is led to believe Lisbon is the killer. Later Roy visits her house and reveals details of the crime only the killer would know. He is revealed to be the real killer and he framed Lisbon by drugging her with the coffee he gave her. This is why he focused on treating her and he completely ignored Jane. He tried to bargain with them about giving up the man who hired him but they already know it was a man named Milton Howard. Milton is revealed to have paid Roy and David through one of his shell companies to frame her so he would go free at his trial.