Preheat oven to 425 degrees
Remove beet greens and discard (or save for another use)
Wrap beets individually in aluminum foil
Roast in oven, on sheet pan, for one hour, until beets are tender
Meanwhile, peel oranges and cut into 1/2-inch segments
Toss romaine, radicchio, diced red onion, and orange segments in a large salad bowl
Once beets are roasted, remove from oven and let cool - about 10 minutes
Remove beets from foil and, running under cool water, use your fingers to remove skins from beets. Skin should easily slide off if beets are thoroughly cooked
Dice beets into 1/2-inch segments and toss with greens and oranges
Drizzle salad with Dijon vinaigrette and toss well