Method
Season chicken
Heat oven to 425°F. Pat thighs dry, rub with olive oil, and season with salt, pepper, smoked paprika and garlic powder.
Make the glaze
Whisk maple syrup, both mustards, vinegar, oil, minced garlic, thyme, rosemary, salt and pepper. Reserve 3 tablespoons in a clean bowl for the final glaze.
Prepare vegetables
Cut potatoes into 1-inch pieces, carrots into thick diagonal pieces and onion into wedges. Toss with oil, salt, pepper and thyme. Spread in a large roasting pan.
Roast vegetables
Roast vegetables uncovered at 425°F for 15 minutes.
Add chicken
Nestle thighs skin-side up among vegetables. Brush with glaze, spoon the main bowl’s remaining glaze over vegetables, and roast 25–30 minutes.
Glaze again
Brush with reserved clean glaze; toss vegetables gently. Roast another 10–15 minutes, until chicken reaches at least 165°F (175–185°F for more tender thighs) and potatoes are tender.
Rest and serve
Rest chicken 5–10 minutes. Spoon pan juices over vegetables, garnish with parsley or thyme, and serve.