What cut of roast? How thick/weight? I would smoke it to medium rare with a liberal (mostly salt & pepper) brisket rub then rest it and reverse sear it for some color. Cut thin against the grain. I used to get bison back home in PA (there was a bison ranch a couple of miles from me) but haven't cooked it in a long time. I'm looking forward to seeing what you do with it.
Whatever you have will be analogous to a cow pretty much, just MUCH leaner. How much it weighs or how thick it is doesn't matter. You wouldn't cook a chuck roast the same way you would a sirloin tip, for example.
So assuming it is "pot roast" and not a prime rib or tri-tip... I still would do it as I mentioned. If you don't like medium rare, of course medium is an option (any more done than that and you might as well do it in the slow cooker ) In all seriousness, you might want to smoke it for flavor and then slow cook it with some vegetables and liquid until fall apart fork tender.