Combine first 3 ingredients in a small saucepan. Bring to a boil; cover and cook 1 minute. Remove from heat, and let stand 30 minutes. Stir in vinegar and rosemary; set aside.
Combine sausage, onion, and sweet potato in a large greased roasting pan. Bake, uncovered, at 450° for 30 minutes, stirring occasionally.
Stir fig mixture into sausage mixture; bake 10 more minutes. Serve warm or at room temperature.