1 Roast for 2 1/2 to 3 hours for spare ribs or 1 1/2 to 2 hours for baby back ribs. Halfway through cooking, cover the ribs with aluminum foil to protect them from drying out.  Brush with barbecue sauce: About 30 minutes before the end of cooking, brush the ribs with barbecue sauce, re-cover with foil, and finish cooking.