Preheat the oven to 425°F (220 ̊C)
Place beets in the center of a large piece of foil. Drizzle them with oil and season with salt and pepper. Tightly seal the foil around the beets to make a packet. Place the packets on a rimmed baking sheet and roast until the beets are tender when pierced with a knife, about 45 minutes to 1 hour, depending on the size of your beets.
Unwrap the beets and let them cool slightly. Remove the skin by peeling it off with your fingers or knife.
While the beets are roasting, toast the hazelnuts on a rimmed baking sheet for 5 minutes, or until they’re golden and fragrant.
Place the toasted nuts on a kitchen towel and rub them against one another to remove the skins then roughly chop the nuts.
Cut a slice off the top and bottom of each orange so they have a flat bottom to sit on. Use a sharp knife to cut the peel and remove as much of the pith from the oranges as you can. Slice the oranges into ¼ inch rounds and use the tip of your knife to pick out any seeds. Set the cut orange slices aside on a prep plate.
To make the dressing, squeeze the juice from half of an orange into a medium bowl. Add the shallot and vinegar. Whisk in the olive oil and season with salt and pepper to taste.
Cut the beets into wedges and toss them with some of the dressing,
Just before serving, divide the yogurt among the plates. Arrange the orange slices and beet wedges over the yogurt, spooning some of the dressing over the top. Sprinkle with the chopped hazelnuts and garnish with mint leaves.