Preheat the oven to 425 degrees and line a baking sheet with unbleached parchment paper.
Cut the butternut squash in half lengthwise, scoop out and discard the stringy fibers and seeds.
Place the squash cut side down on the baking sheet and put the baking sheet into the oven on the center rack.
Roast for about 45 minutes until the squash is cooked all the way through and is easily pierced with a fork.
Remove baking sheet from the oven and let cool for 5 minutes. Then peel the skin from the squash and discard. You can just peel it off with your hands, it'll come right off.
Put the squash into a large mixing bowl with the bananas and cinnamon. Blend until smooth using your Sage Baby Puree & Blend immersion blender.
Serve or store.