The secret to crispy oven roasted potatoes i:s 1) ensure they are super dry before roasting, 2) use plenty of olive oil, 3) spread in an even layer so they are not touching, 4) bake at high heat (425 degrees F) so they outsides caramelize by the time the insides are done cooking. If you use a lower temperature, the potatoes will still cook but they won’t get crispy.