At least 1 hour before cooking, soak wood chips in enough water to cover. Trim fat from sirloin roast. For rub, in a small bowl combine the chipotle chili powder, salt, black pepper, and cumin. Sprinkle rub evenly over meat; rub in with your fingers. Insert a meat thermometer into the thickest part of the meat.

Drain wood chips. For a charcoal grill, arrange medium-hot coals around a drip pan. Test for medium heat above the pan. Sprinkle wood chips over coals. Place beef roast on grill rack above the drip pan. Cover and smoke for 1-1/2 to 2 hours or until desired doneness (meat thermometer registers 140 degree F for medium-rare doneness or 155 degree F for medium doneness). Cover the beef roast with foil. Let stand 15 minutes before carving. (The meats' temperature will rise 5 degree F during standing.) Thinly slice the beef. Place in a covered container and chill up to 24 hours.

In small bowl combine the onion jam and horseradish.

Spread the cut roll tops with jam-horseradish mixture. Place sliced roast beef on roll bottoms. Top roast beef with roasted red pepper strips and arugula; add prepared bun tops. Cover and chill any remaining beef up to 2 days. Makes 12 sandwiches (using 2 ounces cooked meat per sandwich).

Sirloin roast may be smoked ahead and frozen or refrigerated one week prior to event to ease last minute prep time. Beef will also slice easier when it is cold.