Preheat the oven to 400 degrees F. Wash and dry the beets and trim off the ends. Take a large sheet of aluminum foil, 12 by18, and double it over. Put the beets in the middle, drizzle with olive oil and season with the salt and pepper. Bring the sides of the foil up around the beets to make a pouch. Put in the hot oven and bake until the beets are tender, about 1 hour 20 minutes. Remove from the oven and let cool. When cool enough to handle, gently peel off the skin and slice/cut however you like. Chill until ready to use.