when did joe mantegna join criminal minds
On August 11, 2007, Mantegna signed on to replace departing star Mandy Patinkin on the CBS crime drama Criminal Minds.   Since season 9, he has directed several episodes as well.
On April 4, 2015, Mantegna received a Lifetime Achievement Award for Film and Television from The Riverside International Film Festival. 
Later, he is seen sipping a glass of wine at her grave, and next to her grave is shown a gravestone reading “James David Rossi,” with the same birth and death date in 1979, implying David and Carolyn had a son who was either stillborn or had died during or shortly after birth.
In contrast to Hotchner and Gideon, Rossi is decisively extroverted, abrasive, and much less cerebral, though still highly disciplined and focused. In one episode, Emily Prentiss describes him as a “fussy, anal-retentive neat-freak who never leaves anything out of place”, even color-coding his notes (blue pen for evidentiary items, red pen for supposition and theory) E314 . Intelligent and quick-witted, he seems to favor less polished, more traditional police methods in profiling and interrogation – for example, he had no idea what a PDA was E314 . Nevertheless, he, Reid, and Gideon are the only characters who are known for being prolific writers. In later episodes, it is implied that he is more technically savvy than he was when first seen – in “Epilogue”, he attributes his tiredness to a long session of Rock Band and not enough coffee the night before, but claims to have “wiped the floor” with Ringo Starr in the process, apparently on a high difficulty level.
Last week, Matthew Gray Gubler tweeted out behind-the-scenes images from the final episode, too, claiming he and the cast “don’t want to let each other go.”
— matthew gray gubler (@GUBLERNATION) May 8, 2019
Criminal Minds‘ most recent numbers are nowhere near its highest levels. In the 2017-18 season, it still eked into the top 30 most-watched shows on broadcast TV, pulling in an average of 9.58 million viewers. That’s a big fall from the 2008-09 season, when Criminal Minds was the 11th-most-watched show on TV. The numbers just haven’t been big enough to keep the show from being canceled.
For example, Criminal Minds ratings are nowhere near series highs, but in 2017, original cast members Kirsten Vangsness and A.J. Cook signed new contracts and got substantial raises, ones that gave them salary parity with well-paid co-star Matthew Gray Gubler. All those salaries stick out on the CBS ledger, and couldn’t help but play a part in the show being canceled.
Since 2007 he has been cast as a main character of the hit drama series Criminal Minds, as FBI SSA David Rossi, a retired profiler who makes a comeback to the BAU because of some mysterious unfinished business.
Photo and caption, “It’s official now”, from Joe Mantegna’s Twitter.