The best way to make sure you don't get killed by Roger, is to NOT be near him. He uses alot of heavy duty attacks that hit everybody within a few yards of him. What I did was stand about half the length of the Governor's Mansion away from him, and just blast him with Flaming Skull. You could also do that with pistol and grenade, so try to stay spread out the best you can. If you end up aggroing him, then just run around until somebody else manages to pick him up. Keep this up, and you'll be good to go
