- With the rack in the middle position, preheat the oven to 200 °C (400 °F). Line a baking sheet with aluminum foil.
- On the prepared baking sheet, toss potatoes, garlic and rosemary with the oil. Season with salt and pepper. Roast for about 25 minutes or until potatoes are cooked and golden brown. Finish cooking under the broiler for about 5 minutes. Add sausage and cook for 2 minutes. Remove from the oven and let cool slightly.
- In a large bowl, whisk together all the ingredients. Season with salt and pepper. Add the warm sausages and potatoes. Toss in the arugula. Serve immediately.