Preheat oven to 350 degrees F (175 degrees C). Grease 12 muffin cups or line with paper muffin liners.

Place diced sweet potato into a small pan with enough water to cover, bring to a boil, and cook until tender, about 10 minutes. Drain sweet potato; set aside to cool.

Whisk together spelt flour, oats, baking soda, and cinnamon in a bowl. Stir together bananas, oil, and sugar in a separate bowl.

Stir banana mixture into spelt mixture just until dry ingredients are moistened; fold in dates and sweet potato. Divide mixture evenly into 12 muffin cups.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 18 minutes. Cool in pan for 10 minutes; remove to cool completely on a wire rack.