Preheat oven to 400°F and line a large rimmed baking sheet with parchment paper.
In a large bowl, combine kielbasa rounds, potato pieces, bell pepper strips, and onion wedges.
Drizzle olive oil over the mixture, then sprinkle smoked paprika, garlic powder, dried oregano, salt, and black pepper. Toss until everything is evenly coated.
Spread the seasoned mixture in a single layer on the prepared baking sheet, ensuring space between pieces.
Roast for 25–30 minutes, stirring halfway through, until potatoes are tender and browned and kielbasa is heated through and caramelized.
Remove from oven and, if desired, sprinkle with chopped fresh parsley before serving.