Preheat oven to 400°F. Line large baking sheet with non-stick foil and spray with oil (or use a Silpat Mat).
Chop sweet potatoes into bite size pieces about 1-inch cubes and place in large bowl. Stir in pecans, maple syrup, and spices into the bowl. Toss well to coat sweet potatoes and nuts.
Spread sweet potatoes and pecans on baking sheet. Make sure to use a spatula to scrape out all the maple syrup and nuts out of the bowl.
Roast in the oven for 40-45 minutes, until the sweet potatoes are lightly golden brown on edges, stirring once halfway through. Serve warm.