Preheat oven to 425°F. Line a large rimmed baking sheet with parchment for easy cleanup.
Cut potatoes into halves or quarters for even pieces. Pat dry to remove surface moisture.
Toss potatoes with olive oil in a large bowl until lightly coated.
Add 3/4 cup Parmesan, garlic powder, paprika, Italian seasoning, salt, pepper, and red pepper flakes if using. Stir to coat well.
Spread potatoes on the sheet pan, cut sides down and spaced out for browning.
Roast for 20 minutes. Flip potatoes and continue roasting until crisp and golden, 12–15 minutes more.
Sprinkle with remaining Parmesan and parsley. Toss briefly and serve hot.