Preheat oven to 400 degrees.
Place cubed butternut squash and minced garlic on a baking sheet lined with parchment paper. Drizzle with olive oil, tossing to coat evenly. Sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Bake for 30 minutes, or until squash is very tender.
Meanwhile, in a large saute pan, cook sausage until almost cooked through. Sausage will continue to cook in the oven. Set aside and allow to cool as you cook the shells according to package instructions.
Once the sausage has cooled, combine with ricotta and mozzarella cheeses. Add lightly whisked eggs and set aside.
Place blended butternut squash in a saucepan, adding 4 cups of broth. Whisk to combine. Add in 1/2 teaspoon salt and 1/4 teaspoon pepper. Taste sauce, and adjust seasoning to your liking. Allow to simmer for 5 minutes.
In a 9 x 13 pan, add butternut squash sauce, reserving 1 cup to top the stuffed shells. Fill each shell with ricotta and sausage mixture, placing them on top of the butternut squash sauce. Top each stuffed shell with a small spoonful of butternut squash sauce. Cover pan with foil and bake for 30 minutes at 40 degrees.
Garnish with chopped rosemary and sage.