I hardly ever slice up those roasts from the hind quarters.
I poke holes in them and stuff in cloves of garlic. Then dust them with salt, black pepper, cayenne pepper and Chipotle chili powder. Coat liberally with olive oil and massage the seasonings in. And finally, dust the whole thing lightly with all purpose flour and let it sit at room temperature for a bit until the flour becomes fully wetted by the oil.
Put that on the pit over indirect heat and some Hickory chips on the coals and cook to an internal temperature of 125 degrees. That, my man, is GOOD stuff.