With the rack in the middle position, preheat the oven to 200 °C (400 °F).
In an ovenproof skillet, brown the rutabaga and potatoes in the butter. Add the onion and stir. Season with salt and pepper. Bake for about 40 minutes or until the vegetables are tender. Stir a few times while baking.
Prick the sausages with a fork and place in a saucepan of water. Bring to a boil and simmer gently for about 5 minutes. Drain.
In a skillet, brown the sausages in the oil.
Spicy Honey Mustard
Meanwhile, in a bowl, combine all the ingredients. Serve the sausages with the roasted vegetables, honey mustard, and sour cream.