Start by preheating your oven to 400°F (200°C). A well-heated oven will roast the sweet potatoes evenly and help deepen their flavor.

Wash the Japanese sweet potatoes thoroughly. You want to remove any dirt or residues since you’ll leave the skins on for roasting. Use a scrub brush if necessary. Next, let them dry completely on a clean towel. This will help in achieving a crisp exterior when roasting.

Decide if you want to roast the sweet potatoes whole or cut them in halves or quarters. Leaving them whole retains moisture but cutting them increases the surface area, intensifying the caramelization. If you choose to cut them, make uniform pieces to ensure even cooking.

In a large mixing bowl, add the sweet potatoes and drizzle with coconut oil, if using. This step adds a lovely richness and aids in the golden, crispy exterior. Use your hands to coat each piece thoroughly.

Sprinkle salt and pepper over the potatoes. If you have fresh herbs, add those to the mix as well. Toss again to ensure an even distribution of seasoning.

Lay the sweet potatoes on a baking sheet lined with parchment paper, making sure not to overcrowd them. Roast in the oven for about 30-45 minutes, or until the exterior is golden brown and the inside is tender when pierced with a fork. Flip them halfway through the cooking time for even browning.

Once cooked, remove the sweet potatoes from the oven. Allow them to cool slightly before serving. These sweet potatoes can be enjoyed warm as a side dish or at room temperature as part of a salad. They also make a great snack on their own, drizzled with a little honey or maple syrup for added sweetness.