Roadhog synergizes well with pretty much any shield tank. As long as Roadhog has a main tank to complement him, he can more safely do what he does best: get picks. In addition, Roadhog synergizes well with heroes that disrupt shields, since, without shields, his enemies don't have reliable protection from his Chain Hook. So, someone like Doomfist who can punch a Reinhardt to make him drop his shield for a second, or someone who can shred through shields like Bastion or Junkrat are great synergistic picks with Roadhog.