Roast the Vegetables: Preheat your oven to 425°F / 220°C.
In a 13x9x2-inch baking pan, combine the carrots, sweet potato, parsnip, red onion, and garlic.
Drizzle with olive oil, then sprinkle with half of the thyme and all of the pepper.
Toss well to coat everything.
Cover the pan with foil and bake for 20 minutes.
Caramelize and Tenderize: Remove the foil from the pan and give the vegetables a good stir. Return the pan to the oven and bake, uncovered, for an additional 15 to 20 minutes, or until the vegetables are perfectly tender and starting to caramelize at the edges.
Create the Chowder: While the vegetables finish roasting, whisk together the milk, vegetable broth, flour, and the remaining thyme in a large saucepan until completely smooth.
Cook and stir over medium heat until the mixture thickens and becomes bubbly. Gently fold in the hot roasted vegetables, stir for one more minute to heat through, and serve immediately.