Sweet, sour, and peppery all at the same time, this salad is an interesting mix of flavors, textures, and colors.
Preheat the oven to 400 degrees.
If the beets have tops, cut them off and discard or reserve for another use. Place the beets on a large piece of aluminum foil and fold the foil to form a tightly sealed packet. Place the packet on a baking sheet and roast until beets are tender when pierced with a fork, about 1 hour.
Cool the beets slightly. When cool enough to handle, rub off skins with your fingers or a small knife and slice thinly. Peel the oranges, making sure to remove the white pith. Slice into thin disks.
In a large bowl, whisk together orange juice, shallot, oil, vinegar, salt, and pepper. Add the arugula to the bowl and toss to coat. Top the arugula with the beets and oranges. Drizzle with any dressing left in bottom of bowl on top. Season with additional black pepper, if desired.