1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius).
2. Arrange potatoes in a single layer on a rimmed baking sheet that has been rubbed with oil.
3. Cover well and bake for 45 minutes to one hour.
4. Remove tray from oven and uncover. Increase oven heat to 400 degrees Fahrenheit (200 degrees Celsius).
5. Using the back of a glass, smash the potatoes just so that they crack, but are not too flat.
6. Drizzle with oil and sprinkle with salt, pepper, and rosemary.
7. Roast uncovered for about 20 minutes or until potatoes are becoming crispy.
8. Add the sliced sausages and mix.
9. Roast for six to eight more minutes, until sausages start crisping slightly.