In a large bowl, toss potatoes with olive oil, rosemary, and sage until evenly coated. Spread into a single layer on rimmed baking sheet and cover tightly with foil (or with an inverted rimmed baking sheet of the same size). (recipe note #2)
Roast 20 minutes. Remove foil and stir potatoes; return to oven and roast 25-30 minutes more until crisp and golden brown, stirring half way through. Transfer to serving platter; season to taste with kosher salt and serve hot.
Notes
Red Bliss, new potatoes, fingerling potatoes, or other waxy potatoes all work well. Yukon Gold potatoes are also an option.
Take care not to crowd the potatoes or they'll steam and not get crispy.
Dried rosemary isn't a good substitute here. Rubbed sage is an alternative to fresh, but reduce the amount to 2 teaspoons.