Preheat your oven to 400°F (200°C).
Prepare a large sheet pan by lining it with parchment paper or lightly greasing it.
In a large mixing bowl, toss together the frozen pierogies, sliced kielbasa, sliced bell peppers, sliced onion, olive oil, garlic powder, smoked paprika, salt, and pepper.
Spread the mixture evenly on the prepared sheet pan.
Roast in the oven for 25-30 minutes or until pierogies are golden brown and kielbasa is slightly crispy.
Remove from the oven and let cool for a few minutes before serving.