Preheat oven to 400°F (200°C). Line a large baking sheet with parchment paper.
In a large bowl, toss the kielbasa, potatoes, red onion, and bell pepper with olive oil, garlic powder, dried thyme, salt, and pepper until evenly coated.
Spread the mixture in a single layer on the prepared baking sheet.
Roast for 20-25 minutes, or until the potatoes are tender and the kielbasa is browned and slightly crispy, flipping halfway through.
Serve hot.
Notes
This is a versatile recipe. Feel free to add other vegetables like broccoli, Brussels sprouts, or sweet potatoes.