Preheat oven to 400 degrees F (200 degrees C).

In a bowl, toss the beets with 1/2 tablespoon olive oil to coat. Spread in a single layer on a baking sheet.

Mix the remaining 2 tablespoons olive oil, garlic powder, salt, pepper, and sugar in a large resealable plastic bag. Place the sweet potatoes and onion in the bag. Seal bag, and shake to coat vegetables with the oil mixture.

Bake beets for 15 minutes in the preheated oven. Mix sweet potato mixture with the beets on the baking sheet. Continue baking 20 minutes, stirring after 20 minutes, until all vegetables are tender.

meanwhile, make the sauce: Combine all the butter, water, maple syrup, brown sugar, cinnamon, nutmeg, and ginger into a medium saucepan over medium heat. Cook and stir until the butter has melted. Stop stirring and bring to a gentle boil. Boil for 2 minutes without stirring. Remove sauce from heat and stir in the vanilla extract. (And orange zest, if using.)

stir sauce into mixture and continue baking 45 minutes, stirring after 20 minutes, until all vegetables are tender.