Brown roast in oil on all sides in a large skillet; drain. Transfer beef to a 5-qt. slow cooker. Combine the broth, onion, dressing mix, garlic, Italian seasoning and pepper flakes in a large bowl; pour over roast., Cover and cook on low for 8-10 hours or until tender. Remove meat; cool slightly. Skim fat from cooking juices. Shred beef with two forks and return to slow cooker; heat through. Place 1/2 cup on each roll, using a slotted spoon. Serve with pepperoncini and pepper rings if desired.