Place the cut potatoes, beets, onions, garlic, and orange wedges into a bowl. Toss to mix. In a separate bowl, whisk together the reserved orange juice, olive oil, maple syrup, vinegar, and alittle salt and pepper. Taste for seasonings. Pour this over the cut vegetables. Toss to coat.
Spray a large rectangular glass baking dish with olive oil spray. Turn the vegetables into the prepared baking dish. Using a rubber spatula, scrape the bowl of the juices, pouring them evenly over the vegetables. Cover the baking dish tightly with foil. Bake the vegetables for about 30-45 minutes, or until they are fork-tender to your preference.