Preheat your oven to 425 degrees F (220 C). Line a large baking sheet with parchment paper for easy cleanup and better browning.
Pat the sweet potato cubes dry with a clean kitchen towel or paper towels. Removing surface moisture helps them crisp up.
In a large bowl, toss the sweet potatoes with the cornstarch until evenly coated. The cornstarch creates a light crust when roasted.
Add the olive oil, salt, pepper, smoked paprika, garlic powder, and maple syrup or honey (if using). Toss well to coat every piece in seasoning and oil.
Spread the sweet potatoes out in a single layer on the prepared baking sheet. Leave a little space between pieces — crowded potatoes steam instead of crisp.
Roast for 20 minutes, then remove the pan from the oven and gently flip the cubes with a spatula so they brown evenly.
Return to the oven and roast for another 10 to 15 minutes, or until the edges are golden and crisp and the centers are tender when pierced with a fork.
If using fresh herbs, toss them with the hot potatoes immediately after they come out of the oven. Finish with a pinch of flaky sea salt.
Serve warm. These are great on their own, alongside a roast, or tossed into salads and grain bowls.