Preheat the oven to 425°F (220°C).
In a large bowl, combine the baby red potatoes, broccoli florets, red bell pepper pieces, and red onion wedges.
Drizzle 2 tablespoons of olive oil over the vegetables and sprinkle with 1/2 teaspoon salt, 1/4 teaspoon black pepper, and 1/2 teaspoon dried thyme. Toss to coat evenly.
Place the seasoned vegetables on a large rimmed baking sheet in a single layer.
In the same bowl, add the chicken thighs. Drizzle with the remaining 1 tablespoon olive oil.
Sprinkle the chicken with garlic powder, smoked paprika, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon black pepper, and remaining 1/2 teaspoon dried thyme. Rub the seasoning evenly over the chicken pieces.
Arrange the chicken thighs skin-side up on the baking sheet among the vegetables, ensuring they are spaced evenly.
Roast in the preheated oven for 35 to 40 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the vegetables are tender and lightly browned.
For extra crispy skin, broil the sheet pan for 2-3 minutes at the end of cooking, watching carefully to prevent burning.
Remove the sheet pan from the oven and squeeze fresh lemon juice over the chicken and vegetables before serving.