1. Heat oven to 425°F. Place tenderloin on rack in shallow roasting pan. Roast about 30 minutes until internal temperature reaches 150°F. Let stand 10 minutes before slicing very thin.
2. Meanwhile, mix together salad dressing and barbecue sauce; set aside. Sauté onion slices in oil over medium heat until very tender and dark golden brown.
3. Place bottom half of each toasted roll on baking sheet; spread with barbecue ranch dressing. Top with ham, pork tenderloin, caramelized onions, shredded cheese and bacon. Place under broil until cheese is melted, 1 to 2 minutes.
4. Remove from oven, top with arugula and crowns of rolls to serve.