Preheat the oven to 425 degrees F. Slice off the top portion of the garlic head to expose some of the cloves. Place the garlic on a piece of foil. Drizzle lightly with olive oil and wrap in foil. Transfer to the oven and roast until cloves are lightly browned and tender, about 20 minutes. Let cool, then squeeze the garlic out into a bowl. Mash the cloves with a fork. To make the meat sauce. Heat the olive oil in a large pot over high heat. When the oil shimmers, add the chicken sausage and brown all over, about 5 to 8 minutes. Add onion and cook another 2 minutes. Reduce the heat to low, add the tomatoes, 1 cup water, the bay leaf, oregano, and a pinch each of salt and pepper. Simmer for 15 minutes or until the sauce thickens slightly. Remove the bay leaf, stir in the roasted garlic. Taste and adjust seasonings as needed.Meanwhile, poke a few holes into the squash with a fork and place on a plate. Microwave 3 minutes. Let cool slightly, then cut in half lengthwise, scoop out the seeds and discard. In a medium bowl, mix together the milk, ricotta cheese, nutmeg, and basil. Season with salt and pepper. Stir in 1 cup fontina cheese and 1/2 cup provolone cheese. Place the squash in a baking dish and season the cut sides with salt and pepper. Sprinkle the remaining fontina cheese into the bottom of each squash, then evenly divide meat sauce among the squash cavities. Now spoon the milk/cheese mix over the meat sauce. Top with the remaining provolone cheese. Cover the squash loosely with foil. Transfer to the oven and bake 20 minutes. Remove the foil and continue baking another 15-20 minutes or until the squash is tender and the cheese is golden brown on top. The squash will seem a little soupy, this is OK. Let the squash sit 5 minutes, then use a fork to scrape the squash into strands, mixing the meat and cheese with the squash. Serve topped with thyme and sage.