Preheat oven 400*
On a medium baking sheet place diced sweet potatoes. Drizzle olive oil over potatoes, season with salt and pepper and coat evenly.
Bake for 30-45 minutes, until potatoes are crispy on the outside.
Sprinkle potatoes with cumin, brown sugar and chiles.
Toss until sugar is melted and chiles are dispersed evenly.
Place potatoes on plates and garish with cilantro and sour cream, if you choose.