1. Heat oven to 375 degrees F. Wrap beets in a double layer of aluminum foil, seal and then bake until soft, about 75 min.
2. In a bowl toss together carrots, squash, garlic, 2 tbsp olive oil, several thyme sprigs and 1/2 tsp each salt and pepper. Transfer to a rimmed baking sheet. Roast alongside the beets until just tender and golden, 35 to 40 min. Peel skin from cooked beets by rubbing with a paper towel, then cut beets into 1-inch pieces. Set aside.
3. Measure orange juice, then add enough vinegar to equal 2/3 cup. Whisk together juice, vinegar and 1/4 tsp salt and drizzle in 2 tbsp olive oil, whisking constantly. Add thyme leaves and zest. Place vegetables on a serving dish and add orange vinaigrette. Garnish with thyme. Makes 6 to 8 servings.