how long do you roast sweet potatoes
1 If using optional cayenne pepper, sprinkle over sweet potato pieces to taste.  Roast the sweet potatoes until they are tender throughout, but not mushy. At 400 degrees for Â½-inch pieces, this usually takes between 40 to 50 minutes, but I start checking at 30 minutes. Stir pieces once or twice during roasting to promote even cooking.