Preheat the oven to 425°F (220°C).
In a large bowl, combine diced sweet potatoes, olive oil, minced garlic, salt, black pepper, and thyme.
Spread the mixture evenly on a baking sheet lined with parchment paper.
Roast in the preheated oven for 25-30 minutes, stirring halfway through.
Remove from the oven and sprinkle grated Parmesan cheese over the hot potatoes.
Return to the oven and roast for an additional 5-10 minutes until the cheese is melted and golden.
Remove from the oven, adjust seasoning if needed, and serve warm.