Rossi explained the full story to why he left the BAU in Criminal Minds: Evolution

For the longest time, Rossi said that he was fed up of the red tape and wanted to write books. That’s why he left the BAU before Criminal Minds began. Then in a recent episode, Jill Gideon flipped the script.

Jill said that Rossi left because she broke his heart. She implied an affair, and it certainly seemed like that was possible as the two argued in his office. Prentiss decided to question Rossi about it all, getting to the truth of the matter.

Rossi wasn’t truthful about why he left, but Jill certainly manipulated Prentiss’s thoughts. Rossi explained the real reason he left the BAU.

Rossi was in love with Jill in Criminal Minds: Evolution

It turned out that some of Jill’s statements were true. Rossi did love her. And there is a chance that she loved him back. However, they didn’t have a physical affair. It’s clear that it was all emotional.

Rossi shared that he and Jill would turn to each other when Gideon was deep into a case. Everyone will know how Gideon got when it came to cases, and he would always lash out on someone. At the time, there were only the three of them in the BAU, and that meant they would turn to each other.

Rossi then went on to share he didn’t like the way Gideon treated Jill. He thought that Jill deserved better, and he thought that “someone better” was him. However, Jill and Gideon were trying to make their marriage work, and Rossi decided that the only option was to step away.

Eventually, the Gideons divorced. By the time this happened, Rossi was onto his second wife. He never really got over Jill, and there was a hint in the episode that a relationship could start up again. However, Rossi realized that the kiss was Jill’s way of getting Rossi out of the house so she could go about her own plan to get Damien.

So yes, Rossi and Jill had an emotional affair. Rossi did leave because of that. He didn’t betray his friend with a physical affair, though. He left before that could happen.