In a large bowl, combine potatoes, oil, salt and rosemary. Stir so that potatoes are evenly covered in oil, salt and rosemary (or as evenly as you can manage)
Spread potatoes on a large baking sheet.
Roast potatoes for 20-30 minutes depending on how crispy you like them. Stir halfway in between.
Serve hot.
Notes
FREEZER PREP: To make these ahead of time, bring a large pot of water to boil. In the meantime, prepare a bowl with ice cold water (this will be your water bath after the potatoes parboil) Submerge diced potatoes in boiling water and boil for 3 minutes. DO NOT OVERCOOK! Immediately remove from heat and transfer with a slotted spoon to ice water bath. Drain cooled potatoes in a colander. In a large bowl, combine potatoes with olive oil, salt and rosemary. Transfer cooled potatoes to a baking sheet in a single layer. Place in freezer and freeze until firm. Transfer to large storage bag, seal and label.TO PREPARE: Preheat oven to 400 degrees F. Take as many frozen potatoes as you want to prepare and spread on large baking sheet. DO NOT THAW POTATOES! Bake as instructed.