Preheat oven on 450 F. Prepare the vinaigrette: Wisk the mustard, olive oil and lemon juice together; set aside.
Score sausages, being careful not to cut all the way though. Combine potatoes, peppers, onion, and cabbage in a large bowl. Sprinkle with garlic, salt, pepper, paprika and olive oil, and toss until all vegetables are coated with olive oil and seasonings. Spread vegetables on a large sheet pan, then nestle in sausage. Roast sausages and vegetables for 15 minutes on middle oven rack. Turn sausages over and roast for 15 minutes more. Sausages are done when as inserted meat thermometer registers 170 F. Remove sheet pan from oven. Drizzle with the vinaigrette, then sprinkle parsley on top.
Makes 5 to 6 serveings.