Preheat the oven. Set it to 425°F (220°C). Line a large rimmed baking sheet with parchment or lightly oil it. A hot oven ensures crisp skin and caramelized veggies.
Pat the chicken dry. Use paper towels to remove surface moisture from the thighs.
Dry skin is key for crisping. Place the thighs in a large bowl.
Mix the herb oil. In a small bowl, combine olive oil, garlic, thyme, rosemary, oregano, lemon zest, salt, and pepper. Stir into a fragrant paste.
Season the chicken. Spoon about half of the herb mixture over the thighs and rub it under the skin and all over the surface.
This boosts flavor and helps the skin brown.
Prep the veggies. In another bowl, toss potatoes, carrots, bell pepper, and red onion with the remaining herb mixture. Add a drizzle more oil if needed so everything is lightly coated.
Arrange on the pan. Spread the vegetables in a single layer on the baking sheet. Nestle the chicken thighs on top, skin side up, spacing them out so air can circulate.
Roast. Place the pan on the middle rack and bake for 25 minutes.
If using broccoli, toss it with a touch of oil and salt and add it to the pan now.
Finish roasting. Continue baking for another 15–20 minutes, until the chicken skin is deeply golden and the internal temperature reaches 165°F (74°C) in the thickest part (not touching bone). The veggies should be tender and caramelized at the edges.
Broil for extra crisp. If you want the skin extra crackly, broil for 1–2 minutes at the end. Watch closely to avoid burning.
Rest and finish. Let the chicken rest on the pan for 5 minutes.
Squeeze lemon juice over everything and sprinkle with fresh parsley. Serve straight from the pan.