Smaller pieces of beets obviously roast more quickly. Start by cutting both ends of the beets off, and peeling them. Cut them in half end to end, and then in half again, and continue until you have thin wedges. (See photos). Alternatively, you can do a small dice - 1/2" will cook fairly quickly. Roast until tender but not soft. Depending on the size of your beet pieces, this may take 20-30 minutes.