This side dish pairs well with pan-roasted fish or roasted beef or chicken.
Preheat oven to 450 degrees. Individually wrap 4 beets in foil. Place on a baking sheet and roast until tender when pierced with a paring knife, 45 to 60 minutes. Let cool. Rub beets with paper towels to remove skins and cut into small wedges.
Whisk together olive oil, vinegar, and mustard; season with salt and pepper and stir in parsley. Toss beets with dressing. Serve topped with blue cheese and walnut pieces.