1. Preheat oven to 425 degrees F. If using small beets, cut them into 1- to 1-1/2-inch wedges. Place beets in a single layer in a shallow baking pan. Drizzle with 1 tablespoon of the oil; toss to coat. Sprinkle with salt and pepper; toss to combine. Cover with foil and roast for 25 minutes. Uncover and roast about 15 minutes more or until beets are tender; cool. If using small beets, peel the beets. (Baby beets do not need to be peeled.)
2. Meanwhile, using a small sharp knife or citrus tool, remove long shreds of peel from the orange, taking care not to remove the white pith; measure 2 tablespoons peel. Squeeze juice from orange; measure 1/3 cup juice.
3. In a glass dish, whisk together the 1/3 cup orange juice, the remaining 1 tablespoon oil, vinegar, shallot, and Dijon mustard. Add beets and orange peel; toss gently to combine. Cover and marinate at room temperature for 30 minutes or in the refrigerator for up to 8 hours. Makes 8 servings.