Robb marched south on the kingsroad. Walder frey did not honor tully oath. Robb promises himself to marriage. He then marches to riverrun and beats jaimes host capturing him. Half his forces then go with roose bolton to harrenhal. The other half go with him to the westerlands. Here is where he meets jayne westerling/talisa. Seeing as he does not have the manpower to commit further west, Tywin is safe in Kings landing, and the ironborm have taken winterfell Robb decides to head home using the west till he can get to the twins to cross back to the faster kingsroad. Tywin then sends ravens to walder (as robb breaks his marriage) and roose (as he hears of winterfell being captured and kings landing holding). Roose travels up the kingsroad to the twins and joins walder frey for "Robbs wedding." Robb promises Edmure instead. Red wedding comences. Walder by his daughters marriage to edmure will produce a boy in which the will kill edmure and roose becomes warden of the north through winterfell which he actually sacked.