Skins provide structure. They cover and protect what is inside. Skins have flavor. That flavor can be transferred to vegetables, fruit, fish and meat during the cooking process. It is not always easy and convenient to peel an ingredient after it is cooked. Forethought can allow us to cook ingredients in their skins and then peel them for later use. When we do this, generally the ingredient needs to be handled quickly, while still hot, in order to make peeling easier.
Fingerling potatoes that are to be roasted benefit from an initial boiling and then a hot/warm peeling. If done properly, the skins peel off easily leaving 100% of the potato behind. We then cool them down and allow the starch to retrograde. This firms up the potato and allows for it to be roasted uniformly, keeping its shape through the entire process. Of course, if we are making mashed potatoes a different approach may give us better result. A smart solution there is to peel the potatoes in advance and boil the potatoes and skins together to cook them. The skins in this case provide extra flavor. Alternatively the skins may be cooked first with butter to caramelize them and allow them to exchange flavors with the fat. The crisped skins can then be a delicious accompaniment or they can be used to flavor the water used to cook the potatoes for mashing. And then the potatoes can be enriched with the leftover flavored butter when you mash them or roasted in the potato skin butter. You don't need extra ingredients to create more flavor, you just need to use the ones you have to their best advantage.