To roast beets: Preheat oven to 400 degrees. Place scrubbed and trimmed beets on a piece of aluminum foil and rub oil over them with your hands. Sprinkle with salt and wrap tightly inside foil. Transfer foil packet to a baking sheet. Bake until beets are tender (you should be able to insert a knife into the beet with little resistance), about 45 minutes to an hour. Larger beets will take longer to cook than smaller ones. Remove beets from the oven. Once they are cool enough to handle, rub the skins off using a paper towel. Cut each beet into ½ inch cubes.