Preheat the oven to 400°F (200°C).
Slice the sausages into bite-sized pieces.
Chop the bell peppers and onion into strips or chunks.
In a large bowl, combine sausages, bell peppers, onion, garlic, olive oil, Italian seasoning, salt, and pepper.
Spread the mixture onto a sheet pan in a single layer.
Roast in the oven for 20-25 minutes, stirring halfway through.
Let the dish rest for a few minutes before serving.
Serve hot, garnished with fresh herbs if desired.