Preheat oven to 400 degrees. Spray an 18 by 13-inch baking sheet with non-stick cooking spray.
Scrub and rinse potatoes. Cut each potato in half then cut into fairly large wedges (about 8 total per potato). Place potatoes on baking sheet.
Drizzle with olive oil, sprinkle evenly with parmesan, rosemary, garlic powder and season with salt and pepper (about 1 tsp salt 1/4 tsp pepper). Toss lightly. Then spread into an even layer, laying potatoes on one cut side.
Roast in preheated oven for 30 - 35 minutes, turning potatoes to opposite cut side halfway through. Broil during last 1 - 2 minutes to crispen them up more.
Sprinkle with a few more tablespoons parmesan and the parsley. Serve warm.
For the sauce: Whisk together all ingredients in a small bowl. Serve with potato wedges.
*I've tested these with both fresh garlic and garlic powder and I prefer the garlic powder because it doesn't develop that slightly bitter taste from being cooked at such a hot temperature for so long. If using fresh garlic, I recommend tossing it with a tiny bit of olive oil and waiting until halfway through to add it.
Recipe source: Inspired by Ina Garten and The Chunky Chef