In a large saucepan, bring 7 cups of broth to a boil. Cover and reduce heat to low.
Melt the butter in large, heavy pot over medium heat. Add the onion and sauté until tender, about 5 minutes. Add the squash and 1½ teaspoons rosemary; sauté 4 minutes to coat with butter. Add the rice and stir for 2 minutes. Add the wine and simmer until evaporated, about 1 minute. Add 3 cups of hot broth, bring to boil.
Reduce heat and simmer uncovered until the rice is just tender and the risotto is creamy and slightly soupy, adding more broth by ½ cupfuls as needed to maintain consistency and, stirring occasionally, about 18 minutes. Stir in the spinach, cream and Parmesan cheese.
Transfer the risotto to a large bowl. Sprinkle with blue cheese and the remaining ½ teaspoon of rosemary and serve.