Heat the oven. Set it to 425°F (220°C). A hot oven gives you crispy edges and juicy chicken.
Prep the pan. Line a large sheet pan with parchment or lightly oil it.
Use a pan big enough to spread everything out in a single layer.
Make the lemon-herb mix. In a bowl, whisk together olive oil, lemon zest, lemon juice, Dijon, honey, paprika, thyme, rosemary, red pepper flakes (if using), 1 1/2 tsp salt, and 3/4 tsp black pepper.
Season the veggies. Add potatoes, onion, bell pepper, broccoli, and garlic to the pan. Drizzle with about half the lemon-herb mix. Toss to coat.
Spread into a single layer, keeping space in the center for the chicken.
Season the chicken. Pat thighs dry. Rub with the remaining lemon-herb mix, making sure to get under the skin if possible. Sprinkle an extra pinch of salt on the skin for crispiness.
Arrange on the pan. Nestle the chicken, skin-side up, among the veggies.
Don’t crowd the chicken; space helps the skin crisp.
Roast, then toss. Roast for 20 minutes. Pull the pan out, toss the veggies gently, and spoon any juices over the chicken.
Finish roasting. Return to the oven for another 15–20 minutes, until the chicken reaches 165°F (74°C) in the thickest part and the potatoes are tender. For extra-crispy skin, broil for 2–3 minutes at the end, watching closely.
Add fresh herbs. Sprinkle parsley over everything.
Squeeze a little extra lemon on top if you like it brighter.
Rest and serve. Let the chicken rest 5 minutes on the pan. Serve straight from the sheet with any pan juices spooned over.