Preheat oven to 400 degrees. Scrub your beets well and top and tail them. Place the beets on a sheet of foil and drizzle with olive oil, sprinkle with salt and pepper, and wrap the foil up to form a tight packet. Roast in a preheated oven for about 45 minutes, or until fork-tender.
Remove the beets from the oven and set aside until they are cool enough to handle. Peel the skin off with a paring knife, and cut each into 8 pieces.
In a small bowl, whisk together yogurt, feta and lemon zest.
In another small bowl, whisk together 2 tbsp olive oil, the white wine vinegar and 1/2 tsp each of the salt and pepper.
Spread the yogurt mixture onto a large plate.
Arrange the roasted beets and the grapefruit on the plate over the yogurt. Sprinkle with pistachios, drizzle with dressing, and garnish with torn mint leaves.