Preheat your oven to 400°F

If using baby beets, wrap 3 to 4 beets together in foil packets and place them on a baking sheet; if using large beets, wrap them individually in foil and then place on a baking sheet. Roast the beets until they’re tender and a paring knife slips easily into their centers, about 20 minutes for baby beets and 45 minutes for large beets. Remove the beets from the oven and, once cool enough to handle, open the foil packages. Let the beets cool completely.

Meanwhile, peel and segment the oranges. Cut off the tops and bottoms of the oranges so that they sit on the countertop. Using a sharp paring knife slice off the skin from top to bottom, removing the peel and pith so that no white is left on the orange. Slice along each membrane to cut out the individual orange segments. Place the oranges in a large bowl with the onions, olives and mint.

Slip the beets out of their skins and cut them into 1/4-inch thick slices (halve and then slice if using larger beets). Add them to the bowl with the oranges, season with salt and pepper to taste and then drizzle some olive oil and the lime juice over the beets. Toss and serve immediately.