Preheat oven to 200F degrees Place roasts in large roasting pan or Dutch Oven. Do not add salt or water. Cover with a tight lid and roast about 12 hours, until well done. Or cook roasts with 1 cup water in pressure cooker 35 to 40 minutes. Drain meat, reserving juices. Cool meat, then remove bones. Shred meat, and set aside. Melt shortening in a large skillet. Add onions and green chilies. Saute 1 minute. Add green chili salsa, garlic powder, flour, salt and cumin. Cook 1 minute over medium low heat. Stir in reserved meat juices and shredded meat. Cook 5 minutes until thick. Cool.