Preheat the oven to 400°F (200°C).
Trim the tops from the beets leaving about 1” of the stems – do not remove the “tail”. (keeping an inch of the tops and the tails prevents the beets from “bleeding” as they roast)
Wrap the beets, 4 or 5 at a time in a large sheet of foil, closing it tightly.
Place the foil packages on a cookie sheet and roast for 45 minutes to 1 hour depending on the size of the beets. The tip of a sharp knife should slide easily into the beet with little resistance.
Remove the beets from the oven and set aside to cool.
With a small knife cut off the tops and tails and scrape the skin off the beets. (it is best to wear an apron for this job because beet juice stains don’t wash out!)
Cut the beets into ¼” slices or ½” cubes and set aside in a medium bowl.
Slice the tomatoes ¼” thick and place in a large bowl. **See note below