Turn on the oven to 375. If you the oven is on for other purposes sweet potatoes will happily cook anywhere from 300-425, the timing will simply be adjusted. Hotter = shorter time, cooler = longer time.
Leave the skin on the sweet potato and scrub off any crud or dirt. With a paring knife prick it all over, lightly. (Be warned, skipping the pricking will lead to a potato explosion. I speak from the experience of cleaning a sticky mess up.) Once it is cooking, drizzles of sugary syrup are common because of this pricking, but that better than exploding!
Place on a baking sheet or other oven safe dish. Roast for about 25 minutes. Check by squeezing it gently. Size and shape will effect cooking time. Big, fat, round sweet potatoes will take longer. It can easily take up to an hour to cook depending on the size and oven temperature.
Once they are tender to the touch, remove from the oven and set aside to cool. If eating with the skin on, you do not need to cool as long. Simply break it apart, add the butter or coconut oil and sprinkle with salt.
If peeling, cool until you are able to handle it. Placing outside on a cool day or in the fridge briefly will speed this process along. With the aid of a paring knife, remove the skin in thick strips.
Enjoy or mash up with a fork for another recipe.