Preheat the oven to 400°F (200°C).

Wash the beets thoroughly and trim off the stems, leaving about an inch to prevent bleeding.

Wrap each beet individually in aluminum foil and place them on a baking sheet. Roast for 45-60 minutes, depending on their size. A knife should slide easily into the beets when they're done.

While the beets roast, use a sharp knife to slice off the top and bottom of the oranges, then carefully cut away the peel and pith. Hold the orange over a bowl to catch any juices, then slice into rounds or segment by cutting between the membranes.

In a small bowl, whisk together olive oil, balsamic vinegar, honey, Dijon mustard, salt, and black pepper. Add a tablespoon of reserved orange juice if desired. Taste and adjust seasoning.

Let the roasted beets cool slightly, then peel the skins off with a paper towel or your fingers. Slice into wedges or rounds.

Arrange the roasted beet slices and orange segments on a serving platter. Scatter the thinly sliced red onion over the top.

Sprinkle with crumbled feta cheese and chopped walnuts.

Drizzle the dressing evenly over the salad and garnish with fresh mint or parsley before serving.