Trim excess fat from pork (no need to do this if you use the loin like I do). Combine black pepper, salt, cumin, cayenne and paprika in a bowl; rub on roast. Place green pepper and onion into slow cooker, add pork. Combine sauce and brown sugar; pour over meat. Cover and cook on LOW 8 to 10 hours. Serve on rolls or over rice, if desired.