Preheat the oven to 425°F (220°C).
Line a sheet pan with parchment paper for easy cleanup.
In a large bowl, combine sliced peppers, onions, and sausage.
Drizzle olive oil, garlic powder, salt, and pepper over the mixture.
Toss everything together until well coated.
Spread the mixture evenly on the prepared sheet pan.
Roast in the preheated oven for 25-30 minutes, stirring halfway through.
Check for doneness; the sausage should reach an internal temperature of 160°F (70°C).
If using balsamic vinegar, drizzle it over the mixture just before serving.
Serve warm with crusty bread or on a bed of rice for a hearty meal.
