From @JooeCR: If The Rock were to come back, is it probable he would team with his relative Roman Reigns to face Rollins and Ambrose?
That's a nice thought, but it seems like a stretch. If Rock wrestles it's likely only going to be one match at WrestleMania 31. If that happened then I think it would be against Brock Lesnar. There's even a chance it could be against Reigns although a face vs. face match doesn't seem as appealing as a traditional rivalry that Reigns could have. Perhaps WWE could convince Rock to work Elimination Chamber also as a way to team with Reigns, but I don't see it happening anywhere else. I know that Rock has commented about wanting to work with Reigns at some point (he did take a powerbomb from him), but all of that is very questionable at this point. Rock may not wrestle again. If he does, Reigns is a possible opponent rather than a tag team partner.