This is my go-to method of cooking when I have just a couple of beets to roast or when I have purchased several bunches at the farmer’s market and the sizes are quite varied. With this technique, one packet of beets may be removed even if a second requires additional cooking time. Cleanup is extremely easy, too!
Wrap the beets in aluminum foil, keeping a little moisture from washing the beets and drizzling with a couple of teaspoons of olive oil before sealing. If beets are not consistent in size, group and place in individual foil packets with other similar size beets. I wrap three to four medium size beets together, more if the beets are small, and two if the beets are large. This way, the beets will cook in about the same time, but if there is a vast difference in size, the beets can easily be removed from the oven as they are done.
Place the packet(s) on a baking sheet, and roast in the oven until cooked through, approximately 45 to 60 minutes, depending on size. The tip of a knife or a skewer should easily pierce the beet, yet you should feel a hint of firmness towards the center.
Remove from the oven, let cool for 10 minutes, and then peel and slice, dice, or cut into wedges.