Preheat the oven to 425°F (220°C).
In a small bowl, combine chili powder, ground cumin, smoked paprika, garlic powder, onion powder, crushed red pepper flakes, salt, and black pepper to make the fajita seasoning.
Place the chicken breasts on a large rimmed baking sheet.
Drizzle 1 tablespoon of olive oil over the chicken breasts and rub the fajita seasoning evenly onto both sides of each chicken breast.
In a large bowl, combine the sliced red, yellow, and green bell peppers and the sliced onion.
Drizzle the remaining 1 tablespoon of olive oil over the vegetables and toss to coat evenly.
Spread the seasoned vegetables around the chicken breasts on the baking sheet in a single layer.
Place the baking sheet in the preheated oven and roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the vegetables are tender.
Remove the baking sheet from the oven and let the chicken rest for 5 minutes.
Serve the chicken breasts topped with the roasted fajita veggies, garnished with chopped fresh cilantro and lime wedges on the side.