Question: What unsolved case brought Rossi back to the BAU?
Answer: A double-homicide in Indiana
Before Rossi returned to the BAU in Season 3, he was already a decorated—and incredibly wealthy—true crime author. In "Birthright," Rossi shared the real reason behind his return: To close a 20-year-old cold case involving a double homicide.
As the first officer on the scene on the night of a horrendous murder, Rossi found the murdered couple’s three young children. Each year on the anniversary of the murders, Rossi called the kids to let them know that he would never give up searching for the man that committed the crime. To remind him of the promise he made, he carried a charm bracelet given to him by the children’s grandmother.