Preheat oven to 400° F. Prick sweet potatoes several times with a fork and place on a foil lined sheet pan. Roast sweet potatoes for ~45 minutes or until soft, easily pricked with a fork, and beginning to release syrupy liquid. Overcooked is better than under! Add unpeeled bananas and roast for 10 additional minutes.
Let sweet potatoes and bananas stand at room temperature until cool enough to handle.
Using a food processor or hand held immersion blender, puree sweet potatoes, peeled bananas, maple syrup, and pumpkin pie spice. Stir in milk or milk alternative to ensure the mixture is not too thick or dry. Season with salt to taste. Transfer to a 1.5-2 quart casserole dish. Using a spatula, spread to fill dish and ensure a smooth top.
In a medium bowl, combine oil, maple syrup, and pumpkin pie spice. Add oats and pecan pieces. Stir to combine. Sprinkle evenly on sweet potato mixture.
Reduce oven to 375° F and bake for about 25 minutes or until granola topping is golden brown and sweet potato mixture is hot. Enjoy!