Preheat oven to 430°F and lightly grease a baking sheet.
Pierce sweet potatoes a few times with a fork. Arrange them on the tray and roast for about 40-50 minutes, or until tender. (Smaller sized sweet potatoes are cooked through faster, so pierce with a fork after 40 minutes to check, and continue roasting, if needed until soft.)
Quick version: Optionally, you can wrap the pierced sweet potato in a kitchen towel and microwave for 10 minutes until soft.
While sweet potatoes are baking, heat the oil in a pan. Add the onions are bell pepper and sauté until roasted and softened, about 3-5 minutes. Add the garlic and roast for a further minute until fragrant. Sprinkle with salt, pepper or other seasonings to taste. Set aside.
When sweet potatoes are fork-tender, remove them from the oven. Let cool for 5 minutes, or until cool enough to handle. Cut them in half and scoop out the flesh with a spoon, leaving a thin layer of potato inside of the skins. Mash the soft flesh, add roasted onion mixture, beans, corn, salsa, and mix to combine.
Brush the sides of your sweet potato skins with a tiny bit of oil. scoop the filling inside and sprinkle over non-dairy cheese.
Bake for about 5-10 minutes or until the cheese is melted.