Preheat oven to 425 Farenheit. Spray a baking sheet with cooking spray.
Combine the potatoes, olive oil, thyme and pepper in a bowl and turn to coat. Pour the potato mixture onto the baking sheet.
Roast for 25 minutes, stirring occasionally. After the 25 minutes, add the artichokes and onion. Roast for another 20 minutes. Put the potatoes, artichokes and onions into a serving bowl and top with the feta cheese. Serve immediately.