Preheat your oven to 425°F (220°C).
Slice the red onion into thin wedges and chop the bell peppers into strips.
In a large mixing bowl, combine the sliced vegetables with olive oil, salt, pepper, hot chili powder or flakes, smoked paprika, ground cumin, garlic powder, and oregano. Toss until well coated.
Spread the seasoned vegetables out in a single layer on the sheet pan.
Place the sheet pan in the preheated oven and roast for about 20-25 minutes, stirring halfway through.
Once the veggies are roasted, remove from the oven and serve warm.
