Preheat the oven to 400 degrees F.

Add the chopped sweet potato, turnip, and onion to a mixing bowl and drizzle with olive oil, seasonings, and sea salt. Use your hands to toss everything together until it’s well coated. Spread the vegetables over a large cast iron skillet, baking sheet, or casserole dish.

Place the chopped beets in the center of a 12-inch piece of foil. Fold all of the edges onto themselves, creating a secure foil packet (note: beets secrete juice while roasting, so be sure foil packet doesn’t have any openings). Place both the skillet of vegetables and the foil packet in the preheated oven, and roast for 40 minutes, turning the beets and turnips half-way through, or until vegetables are cooked through and golden-brown. If the vegetables are not golden-brown and crispy by the time they have finished roasting, you can move them to the top shelf of the oven and broil them under the high broil setting for 1 to 3 minutes, keeping close watch so vegetables don't burn.

Remove vegetables from the oven. Carefully open the foil packet of beets (some hot steam may release out), and use a slotted spoon to scoop the beets out of the beet juice. Add beets to the skillet with the other veggies and stir to combine. Serve root vegetables alongside your favorite main dish.