Peel butternut squash and chop into 1 inch pieces. Bring cubes to a boil in a large pot of water, cooking for 10-15 min until tender. Drain and let cool, then puree. You can do this step ahead of time, cooking a whole squash and freezing the puree.
Preheat oven to 375 F. In a large frying pan, cook turkey bacon for 2-3 min each side. Remove from heat and once cool, chop into small pieces.
Add olive oil to the same frying pan, then add brussels sprouts, onion, garlic and sage, sauteeing for 4-5 min on med-high heat until veggies are tender-crisp.
Meanwhile at the same time, In a medium-sized saucepan, add butternut squash puree and milk. Bring to a boil at medium heat, then lower heat to med-low. Add parmesan cheese, salt and pepper, stirring to combine well.
Add ravioli to a greased 9x13 oven safe dish. Add bacon and brussels mixture. Cover everything with butternut squash sauce, then top with mozzarella cheese. Bake for 30 min, then serve immediately.