1. Preheat oven to 425°F (220°C).

2. Peel the sweet potatoes and potatoes, then cut into 2.5 cm (1 inch) pieces. Cut the onion into similar size chunks. Cut the bell pepper into 2.5 cm chunks, removing seeds and membranes.

3. Place the sweet potatoes, potatoes, onion, and bell pepper on a large baking sheet. Drizzle with olive oil, sprinkle with salt and pepper, and toss to coat.

4. Place the sausage links on the baking sheet, spacing them evenly.

5. Roast for 25 minutes. Remove the baking sheet, add the cherry tomatoes, and stir the vegetables.

6. Return to the oven and roast for 10 to 15 minutes, or until the vegetables are tender and the sausage is cooked through.

7. While the vegetables roast, toast the walnuts in a dry skillet over medium heat until golden and fragrant, about 3 to 5 minutes. Set aside.

8. Remove the baking sheet from the oven. Sprinkle the grated cheese evenly over the top.

9. Return to the oven for 5 minutes, or until the cheese is melted.

10. Transfer to a serving dish. Sprinkle with the toasted walnuts and chopped fresh basil. Serve immediately.