Prep. Preheat oven to 375 F and line a rimmed baking sheet with parchment paper.
Roast. Toss cubed butternut squash (24 ounces), onions (1 1/2 cups), salt (1 teaspoon), and pepper (1/2 teaspoon) in 2 tablespoons of oil. Spread the veggies in an even layer on a rimmed baking sheet. Drape bacon (4 pieces) over the top of your veggies. Bake in preheated oven for 45 minutes. You'll know they're done once the veggies are soft and start to brown, and the bacon is fully cooked.
Saute. Meanwhile, add the remaining 1 tablespoon of oil to a large stockpot over medium heat. Once the oil is shimmering, add the garlic (2 cloves) and sage (2 tablespoons). Saute until fragrant, about 1-2 minutes. Add vegetable broth (1 1/2 cup) and warm until heated through.
Blend. Ladle soup into a blender, along with your baked veggies and bacon. Alternatively, you can add veggies and bacon to the pot and use a stick blender to combine. Blend the soup until completely smooth. Taste and adjust seasoning to your liking.
Serve. Pour soup into bowls and top with additional bacon crumbles, heavy cream, or sage. Enjoy!