1. Preheat oven to 400°. Divide beets between 2 large pieces of heavy-duty aluminum foil; drizzle with balsamic vinaigrette, and sprinkle with desired amount of salt and pepper. Seal foil, making 2 loose packets.
2. Bake at 400° for 45 to 55 minutes until fork-tender.
3. Let cool 1 hour in packets, reserving accumulated liquid.
4. Bake walnuts at 400° in a single layer in a shallow pan 8 to 10 minutes or until toasted and fragrant.
5. Peel beets, and cut into slices or wedges. Arrange beets on a serving platter or in a bowl. Drizzle with reserved liquid, and sprinkle with walnuts. Garnish, if desired.