Preheat the oven and roast the beets until tender.

Allow the roasted beets to cool, then slice into wedges.

In a large bowl, combine mixed greens, sliced beets, pistachios, and red onion.

In a separate bowl, whisk together olive oil, apple cider vinegar, honey, horseradish, salt, and pepper to create the dressing.

Drizzle the dressing over the salad and toss gently to combine.