Brush roast with olive oil; rub on the chili powder, oregano, cumin, salt and pepper. Set the roast on one side of barbecue preheated to medium-high. Turn the heat off under the roast, but leave the other flame on medium-high. Close lid and cook about 40 min., or until internal temperature reaches 145F (63C) for medium-rare or 160F (71C) for medium. Transfer roast to platter or cutting board and tent with foil 10 min.
Meanwhile, make dipping sauce by combining beef broth, barbecue sauce, red wine, mustard and garlic in saucepan. Gently simmer 5 min.
Thinly slice the beef, pile onto buns and serve with bowls of dipping sauce.
Tip: Also can use top sirloin roast.