All-purpose potatoes, such as Yukon gold, purple and white potatoes, are best for roasting. They are moister and hold their shape through the cooking process better than high-starch potatoes.
There are three general categories of potatoes: starchy, waxy and all-purpose. Starchy potatoes contain cells that separate when cooked, readily absorbing water during cooking or milk and butter when mashing. They are best for frying and mashing. Russet and most sweet potatoes are categorized as high-starch. Waxy potatoes have a more cohesive cell structure that allows them to hold their shape well when cooked. They are best for soups and salads. Examples of waxy potatoes include red-skinned and fingerling potatoes.