Start by preheating your oven to 400°F (200°C). Line a large, rimmed baking sheet with parchment paper or aluminum foil for easy cleanup. This ensures that the maple glaze doesn’t stick to the pan during the roasting process.
In a small mixing bowl, whisk together the maple syrup, Dijon mustard, olive oil, minced garlic, dried thyme, salt, and pepper. Stir until the mixture is smooth and well combined. This glaze will act as both a marinade and a sauce.
Place the chicken thighs, halved Brussels sprouts, and cubed sweet potatoes onto the prepared sheet pan. Pour the glaze over everything. Use your hands or large tongs to toss the chicken and vegetables until every piece is thoroughly coated in the sauce. Spread them out into a single layer, ensuring the chicken pieces aren’t covered by vegetables.
Slide the baking sheet into the oven and roast for 25 to 30 minutes. If you are using bone-in chicken, you may need an extra 5 to 10 minutes. The chicken should reach an internal temperature of 165°F (74°C), and the vegetables should be tender and slightly charred at the edges.
Remove the pan from the oven. Let the chicken rest for 5 minutes before serving to keep the juices inside. If desired, garnish with fresh parsley or extra black pepper before bringing the pan to the table.