Preheat oven to 450 degrees F. Place cubed butternut squash on a rimmed baking sheet and coat evenly with olive oil. Season with salt and pepper and place 2-3 sprigs of fresh rosemary on the sheet. Place in oven and bake for 25 minutes, stirring once halfway through.
Meanwhile, in a skillet, cook the three slices of bacon. Place cooked bacon on the side, and reserve only 1 Tbsp. of bacon fat in the pan, discarding the rest.
Heat skillet to medium high heat and add leeks and mushrooms. Season with salt, pepper, ground sage, and 1 tsp. of finely chopped fresh rosemary. Cook for 5-7 minutes or until mushrooms are tender.
Add cooked butternut squash to the skillet and stir to combine for 2 minutes.
Remove from heat and top with crumbled bacon and the fresh chèvre cheese. Serve hot.