Roose ended up betraying the Starks and the North by teaming with Walder Frey and Tywin Lannister. He saw to it that Lady Catelyn, Robb, and Talisa Stark did not escape the hall at the Twins.
Easy on the eyes and a man with almost as much honor as his father, Robb really did himself in when he broke his promise to marry one of Walder Frey's daughters and married Talia instead.