Preheat the oven to 400°F. Line a roasting pan with foil; set aside. In a very large bowl whisk together the apple cider, oil, vinegar, mustard, honey, thyme, and salt. Add carrots and parsnips and toss to coat. Transfer vegetables and liquid to the prepared roasting pan; spread in an even layer.
Roast, uncovered, for 35 minutes or until vegetables are tender and liquid has evaporated, stirring twice during roasting.