Preheat oven to 350°F (175°C). Line a muffin tin with paper liners.
In a large bowl, mix together the mashed sweet potatoes, vegetable oil, eggs, and vanilla extract.
In another bowl, whisk together the gluten-free flour, sugar, brown sugar, baking powder, baking soda, salt, cinnamon, and nutmeg.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the chopped pecans.
Divide the batter evenly among the muffin cups.
Bake for 25 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.