Preheat the oven to 425°F (220°C) and place a rimmed baking sheet in the oven to get hot. Cut sweet potatoes into even 1/2–3/4-inch cubes.
In a large bowl, combine the sweet potato cubes with oil, salt, pepper, smoked paprika, garlic powder, and cornstarch (if using). Toss to coat evenly and pat cubes lightly if they feel wet.
Carefully remove the hot baking sheet and spread cubes in a single layer with space between pieces. Roast 20–25 minutes, flipping once halfway through.
For extra crispness, increase the oven to 450°F (230°C) for the last 3–5 minutes or broil for 1–2 minutes while watching closely to avoid burning.
Remove from oven, garnish with parsley or cilantro, and add optional finishes like a squeeze of lime, a drizzle of honey, or grated Parmesan. Serve hot.
Notes
Avoid overcrowding the pan to prevent steaming.
Cornstarch is optional but helps create a light, crispy exterior.
Reheat in the oven to regain crispiness rather than using a microwave.