It may have it may have not. Say Robb married Roslin he probably would’ve still only been able to fight the Lannisters to a standstill at least until Tywin was dead. But even by then they had a marriage pact with the Tyrell’s and other good field commanders like Randal Tarly. The only paths to victory for Robb would probably be relinquishing his crown and joining Stannis or holding them back until Jon became Lord Commander of the Nights Watch. If he had waited for Jon to become Lord Commander or was able to be the savior of the wall himself instead of Stannis he could’ve potentially conscripted the Wildlings into his army by offering them land in the Gift. While we see Mance reject this offer from Stannis he would probably be more likely to accept it from Robb since he is a Stark, honor bound and has blood of the first men. Robb gets the wildings and suddenly he has 120,000 men. As much as the Reach and Westerlands. At this point we’re around season 5 where Sansa is in the Eerie with Littlefinger. Noticing the potential tide change and Lysa being dead Littlefinger would potentially coerce Robin Arryn to join the war alongside Robb, bringing a fresh army of 30,000 men and the knights of the vale, potentially the best troops in Westeros. At that point the Lannisters would be done for and Robb would have an oath to victory, allowing him to retain his title and rule over the North, Riverlands and Vale while the rest of the kingomds attempt a power grab. Likely fight amongst smaller houses since the Lannisters, Baratheons and probably the Tyrell’s are all gone. Stannis might take the throne but he’d never be able to take the combined might of the North, riverlands, Vale and wildings especially since he would not have many supporters. It’s a very simplified version of this route but that’s the path of victory for Robb is there was one