Preheat oven to 450 degrees F, placing 2 shallow baking pans in the oven as it preheats. Drizzle one of the pans with 1 tablespoon of the oil. Carefully arrange vegetables and garlic in one layer in the oiled pan (do not crowd the pan). Drizzle with remaining olive oil and sprinkle with thyme, salt, and pepper. Carefully place the remaining hot pan over the vegetables, bottom side down. Place a heavy skillet or foil-wrapped brick on top of the stack. Roast for 25 to 30 minutes or until vegetables are browned and tender.