Rub beef with the coarse salt and black pepper. Brush with oil. Combine ground ancho peppers or chili powder and cocoa powder in a small bowl. Rub mixture into beef, evenly coating the entire surface.
Prepare grill for indirect grilling. Test for medium heat above drip pan. Place roast on the grill rack, bone side down, directly over drip pan. Cover and grill for 2 to 2-1/4 hours or until an instant-read thermometer inserted into thickest portion reads 155 degree F for medium doneness, turning roast occasionally. Cover and let stand 15 minutes. Cut into individual portions; top with Grilled Papaya Butter. Makes 12 servings.
Grilled Papaya Butter: Peel and seed 1/2 of a small papaya; cut into thick slices. Lightly brush slices with cooking oil. Grill papaya slices over medium-high heat for 5 minutes, turning once. Set aside. Soften 1 pound salted butter (no substitutes). Finely chop papaya; stir into butter. Spoon mixture onto a sheet of plastic wrap. Roll into a log, twisting ends closed. Chill for 2 hours or until firm. Cut into 1/4- to 1/2-inch-thick slices to serve. Reserve remaining papaya and papaya butter for another use.