In a large mixing bowl, combine the cubed sweet potatoes, grapeseed oil, salt, chili powder, garlic powder, and black pepper. Mix well until the potatoes are evenly coated with the spices and oil.
Spread the seasoned potatoes onto a rimmed baking sheet, ensuring they are in a single layer.
Place the sheet in the preheated oven and bake for about 30 minutes. Halfway through, toss the potatoes on the pan to ensure even cooking. Continue baking until the potatoes are golden brown and tender.