Preheat the oven to 400°F (200°C). Place the cubed beetroots on a baking tray, drizzle with olive oil, and season with salt and pepper. Roast for 30-45 minutes until tender.

In a mixing bowl, whisk together olive oil, balsamic vinegar, honey, minced garlic, salt, and pepper until well combined.

In a large bowl, combine the roasted beetroots, mixed greens, feta cheese, and walnuts. Drizzle with dressing and toss gently to combine.