Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel the carrots and parsnips, then dice them into uniform 1-inch cubes for even roasting.
In a medium bowl, toss the root vegetables with the sea salt, black pepper, and one teaspoon of the rendered duck fat found in the confit packaging.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 20-25 minutes until tender and slightly caramelized.
While the vegetables roast, place the duck legs skin-side down in a cold cast-iron skillet.
Turn the heat to medium and sear the duck legs for 8-10 minutes without flipping, allowing the fat to render and the skin to become deeply crispy.
Flip the duck legs and cook for an additional 2 minutes just to warm the meat through.
Arrange the roasted carrots and parsnips on a plate, top with the crispy duck legs, and garnish with fresh thyme leaves.