375° Roast beets and garlic until cloves are soft, about 45 minutes. Remove from oven; unwrap. Rinse beets with cold water; peel when cool enough to handle. Squeeze garlic from skins. Place beets and garlic in a food processor. Add garbanzo beans, lemon juice, tahini, cumin, cayenne pepper and remaining olive oil, salt and ground pepper. Process until smooth. If desired, pulse 2 tablespoons Greek yogurt with beet mixture, dolloping remaining yogurt over finished hummus. Sprinkle with dill or parsley. Serve with assorted vegetables and pita bread.