Preheat the oven to 425°F (220°C).
In a large bowl, combine the halved baby red potatoes, red bell pepper pieces, yellow bell pepper pieces, and red onion wedges.
Add 1 tablespoon of olive oil, 1/2 teaspoon salt, 1/4 teaspoon black pepper, and 1/2 teaspoon garlic powder to the vegetables. Toss well 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, remaining 1 tablespoon olive oil, 1/2 teaspoon garlic powder, 1 teaspoon smoked paprika, 1 teaspoon dried thyme, 1/2 teaspoon salt, 1/4 teaspoon black pepper, and crushed red pepper flakes. Toss to coat the chicken evenly with the seasonings.
Arrange the chicken thighs skin-side up on top of the vegetables on the baking sheet, leaving space between each piece.
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 golden.
If desired, broil for an additional 2 to 3 minutes to crisp the chicken skin further, watching carefully to avoid burning.
Remove the sheet pan from the oven and sprinkle the chopped fresh parsley over the chicken and vegetables.
Let rest for 5 minutes before serving.