If you don't have a microwave, or would like to make more than 2 servings at once, you can bake the sweet potatoes in an oven instead. Preheat the oven to 400°F (200°C). While the oven heats up, wash and dry your sweet potatoes, then poke a few times with a fork. Place the sweet potatoes directly on a baking sheet or baking rack in the preheated oven. Depending on the size of your sweet potatoes, they'll need to roast for 40-60 minutes. Smaller potatoes will cook faster than larger ones.