01 - Preheat oven to 425°F. Line a large rimmed baking sheet with parchment paper or foil to facilitate cleanup.
02 - Slice all bell peppers and the red onion into strips. Arrange them on the prepared baking sheet.
03 - Drizzle olive oil over the vegetables. Evenly sprinkle dried oregano, dried basil, garlic powder, smoked paprika, kosher salt, and black pepper. Toss gently to coat all pieces.
04 - Nestle the Italian sausages among the seasoned vegetables on the baking sheet.
05 - Place the baking sheet in the preheated oven and roast for 25 to 30 minutes. Flip the sausages and stir the vegetables halfway through. Cook until sausages reach an internal temperature of 160°F and vegetables are tender and caramelized.
06 - Remove from oven, garnish with chopped fresh parsley if desired, and serve hot. This dish pairs well on its own, in hoagie rolls, or over rice or pasta.