The events of the Red Wedding effectively end the conflict between House Stark and House Lannister in a decisive victory for King 
Joffrey Baratheon and House Lannister. Not only was Robb Stark himself killed in the betrayal, but the entire Northern army that Robb Stark led to southern Westeros was also destroyed - save only for those forces of 
House Karstark which had earlier abandoned Robb to return home, and the forces of 
House Bolton which turned on the other Northern Houses. For his part in the betrayal, Lord Frey was granted the castle of Riverrun and promised Lannister protection from any northern retaliation. Lord Walder had his men capture 
Edmure Tully out of his marriage bed alive, as 
Riverrun has not yet fallen to Lannister forces and Lord Edmure is a valuable hostage to hopefully negotiate its surrender in the near future. Roose Bolton, for his part in the Red Wedding, is awarded the title of 
Warden of the North, drastically elevating his House's stature.
[2]The Boltons are also granted the lands of 
Winterfell itself.
[4]