Cady McClain's last appearance in Oakdale as Rosanna was in July of 2005. During that time, she discovered the truth about Jennifer and Gwen's baby. When she confronted Craig about it, and he confessed to switching the babies, Rosanna dashed of the house, got in her car and headed for the police station. Craig immediately knew where she was going, so he hopped in his car and chased Rosanna down. In an attempt to get her to pull over and talk to him, he ran her off the road causing her to crash! The crash landed her in a comma, which she never awoke from.
Be sure to watch ATWT in July when Rosanna awakens from her comma and returns to Oakdale. It should be exciting!