Heat the oven to 425°F (220°C). Place a heavy baking sheet in the oven as it heats so the potatoes will begin browning as soon as they hit the hot surface.

Scrub the potatoes well and cut them into 1- to 1 1/2-inch pieces. Small baby potatoes may be left whole or halved, depending on their size.

For the crispest texture, simmer the potatoes in salted water for 7–10 minutes, until the edges are just tender. Drain thoroughly, let them steam-dry, and gently shake them to roughen the surfaces; 1/2 teaspoon baking soda may be added to the cooking water for extra surface texture.

Toss the dry potatoes with olive oil, kosher salt, black pepper, garlic powder, and the optional dried rosemary or Italian seasoning. Make sure every piece has a light coating of oil and seasoning.

Carefully spread the potatoes in a single layer on the hot baking sheet, preferably with the cut sides facing down. Leave space between pieces because a crowded pan traps moisture and prevents deep browning.

Roast for 35–45 minutes, turning the potatoes once after about 25 minutes. Continue roasting until the outsides are deeply golden and crisp while the centers are tender when pierced with a fork.

Transfer the roasted potatoes to a serving dish and finish with chopped fresh parsley. Taste and add an additional pinch of salt if needed, then serve hot.