The flavor of the beets in this salad is measurably better when you roast them whole; then cut them up. The dressing is only a little sparky, even with the harissa-Tunisian hot chili sauce, available in specialty markets. (It is also good on roasted yams or fennel.) When it comes to looking great on a buffet table, few other vegetables beat out beets.
Trim off the greens and stems on the beets; then wash the beets well. If they are small, place 2 or 3 on a square of aluminum foil and wrap; larger beets should be wrapped individually. Place the packets on a baking sheet and roast until tender, about 45 minutes. Remove from the oven and let cool in the foil.
Make the dressing: Pour the orange juice in a medium bowl, and stir in the remaining dressing ingredients, and continue stirring until well combined.
Peel the beets and dice into bite-sized pieces. Put in a serving bowl, pour the dressing over them, and toss gently to combine.