In a small mixing bowl, stir together olive oil, garlic, and thyme. Place potatoes in a mound on baking sheet, pour mixture over potatoes and season with salt and pepper to taste and toss to evenly coat. Spread into an even layer.
Roast in preheated oven until tender, tossing once halfway through, about 30 minutes total (you can broil during last 1 - 2 minutes near broiler for more golden brown potatoes).
Remove from oven, drizzle and toss with more olive oil, then immediately sprinkle with parmesan (if you'd like to fully melt the parmesan just return to broiler for about 1 minute). Sprinkle with parsley and serve immediately.
Notes
Make sure the sweet potatoes are distributed evenly on the baking sheet. If you overcrowd the sheet, the potatoes will steam instead of roast.
For more golden brown potatoes, broil them for the last 1 to 2 minutes in the oven.
If you'd like to fully melt the Parmesan cheese before serving these potatoes, return them to the oven and broil them for 1 minute.