1. 1. Preheat the oven to 400°F (200°C).

2. 2. Wash and peel the red beets, then cut them into cubes.

3. 3. Toss the beet cubes with olive oil, salt, and pepper.

4. 4. Spread the seasoned beets on a baking sheet and roast in the oven for 30-40 minutes until tender.

5. 5. In a serving bowl, combine the roasted beets with mixed greens, feta cheese, walnuts, and balsamic vinaigrette.

6. 6. Toss everything together until well combined.

7. 7. Serve the salad immediately and enjoy!