"Criminal Minds" has been on air for over a a decade, but it is no stranger to cast changes and new faces. When season 12 premieres, fans will say goodbye to Thomas Gibson, who has played Aaron Hotchner since the series' inception, and hello to Adam Rodriguez.

Rodriguez will play Luke Alvez, the head of the Fugitive Task Force. He will permanently join the BAU team as they hunt down the five serial killers still on the run. As fans know, the previous season saw 13 serial killers escape from jail. Eight have been caught, which means the team still needs to rally up the forces because five are still loose, including Mr. Scratch.

Showrunner Erica Messer has talked about Rodriguez's character, as well as the departure of Shemar Moore, who brought to life the character of Derek Morgan since the beginning.

"The fun thing about that character is, not that he's a new [Derek], but what is Garcia going to think of the new guy? There's something real in the workplace environment where a friend leaves and you're like, 'I'll never love anyone the way I loved that friend,' so she has to warm up to him," she said to TVLine.

As for Gibson, his physical altercation with a writer on set resulted in his dismissal from the series. His last appearance is in the second episode of the upcoming season. However, two familiar faces will be returning to the show for good, so fans need not worry about a shortage in cast members.

Paget Brewster, who plays Emily Prentiss, and Aisha Tyler, who plays Dr. Tara Lewis, are both reprising their roles for the new season. However, they have signed on as series regulars this time around. On the other hand, Sherilyn Fenn from "Twin Peaks" will be guest starring as a character related to an UnSub in the third episode of the 12th season.

"Criminal Minds" season 12 will premiere on Sept. 28 at 9/8c on CBS.