• Preheat oven to 400F. Coat beets lightly with oil. Wrap beets, individually (to avoid colour bleeding) in aluminum foil, place on a baking sheet, and roast in the oven until cooked through, approximately 40 to 50 minutes.
• Let cool for 10 minutes, and then carefully peel and slice into ¼-inch thick slices.

For dressing:

• In a medium bowl, whisk vinegar with Dijon mustard, honey, salt and pepper.
• Next, while continuously whisking, pour in olive oil in a light, steady stream. Continue to whisk until olive oil is incorporated into vinegar and dressing has thickened, about 30 seconds.

To assemble salad:

• In a large bowl, toss romaine with arugula, radicchio, feta, onion, walnuts and roasted beets. Slowly add dressing, reserve remaining dressing in the fridge if not all used.