Preheat oven to 425 degrees. Place the cider in a saucepan and bring to a boil. Boil for 15 minutes or until reduced by about half.
Meanwhile, prepare all the vegetables and place them in a single layer on a large rimmed baking sheet. Drizzle with the oil and toss to coat. Drizzle cider over vegetables. Scatter butter pieces over the top and sprinkle with salt and pepper.
Cover tightly with foil and bake until vegetables are almost crisp-tender, about 25 minutes. Remove foil and stir vegetables to coat with the pan juices. Bake uncovered about 15 minutes or until vegetables brown and some of the juices evaporate. Transfer mixture to a serving bowl along with accumulated juices. Sprinkle with thyme leaves and season to taste with salt and pepper.