Preheat oven to 450 F. Use the same baking sheet lined with parchment paper from the croutons.
Wash beets, leave the skin on. Make sure to dry well to avoid excess moisture. Trim the top, slice in half lengthwise.
Put in a bowl and toss with olive oil, Kosher salt and seasoning of your preference (herbs, spices, or simply just salt and pepper).
Place the beets face down on the baking sheet, do not overcrowd.
Roast on the middle rack in the oven for 20 minutes. Rotate the sheet and check every 5 minutes until the beets are done. They are ready when edges are crisp and golden, and the center is tender and moist.