Special Agent David Rossi (Joe Mantegna) is a seasoned profiler who previously worked for Supervisory Special Agent and Unit chief Aaron Hotchner (Thomas Gibson) when the Behavioral Analysis Unit (BAU) was first established. Rossi had retired and was working as an author and an expert lecturer in Criminal Analysis. After Unit Chief Jason Gideon (Mandy Patinkin) left the BAU, Rossi decided to return to the Bureau as a volunteer. At first there was some friction between Hotchner and Rossi over procedure, but Rossi remained dedicated to the unit.
Rossi had an ulterior motive for returning and finally admitted he wanted to work on a case that had gone unsolved for many years. The case centered on three children who had witnessed the brutal axe murder of their parents. Rossi made a promise to the kids that he would find the "unknown subject" who committed the crime. It had been one of his first cases, and he still carried a charm bracelet with the names of the children engraved into it. Over the years, Rossi maintained a relationship with the kids and continued to contact them during holidays and reiterate his commitment to find the killer who savagely stole the lives of their parents. Rossi developed a good working relationship with Penelope Garcia (Kirsten Vangsness), who helped him solve the case. He even went so far as to keep working with the unit after the killer had been found, even though he no longer has any open cases.
Rossi is from a small town called Commack, on Long Island, New York. Although he had a childhood friend, named Ray Finnegan (William Sadler) who became a criminal, Rossi himself had too much integrity to be tempted by the easy money and instead enlisted in the Marines. He was recruited by the FBI after he was discharged from the military and as a result, severed the connections with his past. Because of this, Rossi missed the funeral of his first love, Emma Taylor (Fictional Memory), when she died in 2009. Rossi boasted he "wrote the book" on hostage negotiation when he assumed the role of negotiator in order to free Dr. Spencer Reid (Matthew Gray Gubler), and Agent Emily Prentiss (Paget Brewster). Rossi had a long career at the bureau and enjoys a legendary reputation among the younger analysts, he also had a reputation for getting romantically involved with several women at the bureau. Rossi is a wealthy man, he has been married and divorced three times, maintains being a catholic and pursues a continued relationship with his priest even though he no longer regularly attends church services. Rossi flaunts his wealth and wears only Italian suede shoes, but we get a glimpse at his true personality when he gives $500 to a girl he doesn't know to commemorate her first communion.
"My ex-wife says I have a flair for the dramatic."
"She was the one who got away."
"Now your face is going to be on one of those tapes. When I find it, I'm going to paper the city with it, just like you did with those women. Everyone will see it. They won't be able to ignore you now. But you won't inspire fear, you'll inspire hatred and ridicule because the only power someone like you has is a mask. Once that mask is removed you'll be as insignificant as you've always been. A loser!"