Combine chili powder, cumin, salt and cayenne pepper. Rub over surface of roast. In large skillet, heat oil over medium-high heat. Add roast and sear on all sides.
Place roast, peppers and onions in a 5-quart slow cooker. Add broth. Cook on HIGH 4-6 hours or LOW 8-10 hours or until roast falls apart easily when shredded with a fork.
Remove roast; allow to cool slightly. Drain off liquid, reserving peppers and onions.
Shred roast and place back into slower cooker with peppers and onions. Add in barbeque sauce. Continue cooking on LOW 1 hour. Serve on rolls.