Preheat the oven to 450 degrees F.
Toss the cubed butternut squash in olive oil, sprinkle with salt and pepper and place on a baking sheet. Roast until slightly caramelized, about 20 minutes. (This can be done ahead.)
Melt the butter in a heavy, large pot over medium heat. Add the onions and saute until tender, about 5 minutes. Add the squash and 1 1/2 teaspoons rosemary; saute 5 minutes to coat with the butter and soften. Add the wine and simmer until evaporated, about 1 minute. Stir in the stock, cream and Parmesan. Season with salt and pepper. Simmer on low heat.
Cook the pasta in salted boiling water until al dente. Drain. Add the hot pasta to the sauce and mix well. Toss in the spinach and sprinkle with the blue cheese.
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