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