Preheat oven to 425 degrees.
In a small bowl combine smoked paprika, sugar, ancho chili powder, cinnamon, garlic and salt.
Place sweet potatoes, onions and peppers on a large sheet tray. Drizzle with melted butter and sprinkle with seasoning. Thoroughly toss to coat potatoes.
Place in oven and bake for 30 minutes, or until potatoes are cooked through, and are slightly brown around the edges. Stir potatoes halfway through bake time to ensure even cooking.
Alternative Cooking Method: Do you have the grill fired up? Why not create a foil packet and cook your whole meal at the same time! Simply cut a large piece of heavy duty foil (18×22-inch) and place sweet potatoes, seasoning and melted butter on top. Fold over edges to seal and place on a medium temperature grill. Turn foil packet over several times during grilling to ensure even cooking. Grill sweet potatoes for 30 minutes, or until potatoes are cooked through and slightly brown around the edges.