01 - Preheat the oven to 425°F. Line a large rimmed sheet pan with parchment paper or foil for easy cleanup.
02 - In a large bowl, combine bell peppers, onion, and garlic. Drizzle with olive oil and sprinkle with oregano, basil, crushed red pepper flakes if using, kosher salt, and black pepper. Toss thoroughly to coat evenly.
03 - Spread the vegetable mixture evenly on the prepared sheet pan. Nestle sausages on top of the vegetables.
04 - Roast for 25 to 30 minutes, flipping sausages and stirring vegetables halfway through cooking. Continue until sausages are browned and cooked through (reach an internal temperature of 160°F) and vegetables are tender with slight caramelization.
05 - Optionally garnish with fresh parsley. Serve immediately with crusty bread or over cooked rice.