Preheat Your Oven
Set the oven to 425°F (220°C) to ensure the potatoes roast to a golden crisp. A hot oven helps the skins get that perfect crunch.Prepare the Potatoes
Wash the purple potatoes thoroughly and cut them into halves or quarters to ensure even cooking. Keeping pieces similar in size makes roasting predictable.Toss Potatoes with Oil and Seasoning
In a mixing bowl, combine the potatoes with olive oil, salt, pepper, minced garlic, and rosemary. The oil coats for even browning and the seasoning infuses flavor right from the start.Arrange on a Baking Sheet
Spread the potatoes out in a single layer on the baking sheet, skin side down if you like crispier skin. Crowding causes steaming instead of roasting, which you do not want.Roast in Oven
Place the sheet in the preheated oven and roast for 35 to 40 minutes, flipping once halfway through. This flipping ensures all sides get that irresistible crisp edge.Check for Doneness
Test by piercing with a fork; the potatoes should be tender inside with a crunchy outside. Undercooked potatoes are tough and overcooked ones get mushy.Final Seasoning
Remove from oven and sprinkle a pinch more salt or fresh herbs if desired. Fresh seasoning at the end brightens the flavors.Serve Warm
Serve immediately to enjoy the contrast of crispy skins and fluffy interiors. These potatoes do not wait around for reheats unless you love soggy skins.Pro Tip: Toss the potatoes with olive oil and herbs before roasting—not after—so every bite is flavorful and not dry.