Heat oven to 400°F.

Toss squash with 2 tablespoons oil and season with salt and pepper. Arrange squash in a single layer on a baking sheet and roast until fork-tender, 20–25 minutes. Reserve ½ cup roasted squash, then transfer remaining squash to a high-powered blender or food processor. Add wine, ½ cup broth, and turmeric to blender and purée; season with salt, pepper, and nutmeg and reserve.

Heat remaining 5½ cups broth in a saucepan. Bring to a simmer, covered, over medium-low.

Heat butter in a Dutch oven or stock pot over medium. Add shallots and cook until softened and translucent, 3 minutes. Add rice, and cook, stirring constantly, until edges start to become translucent, 3–4 minutes.

Stir 1 cup warm broth into rice, and cook, stirring constantly until liquid has been absorbed, 1–2 minutes. Stir in remaining 4½ cups warm broth, reduce heat to medium-low, cover, and simmer 16 minutes stirring twice.

Remove lid, add reserved squash mixture, Parmesan, and 2 tablespoons minced sage to risotto; stir until creamy, 3–4 minutes.

Heat remaining 2 tablespoons oil in a skillet over medium until shimmering, add remaining sage and cook until sage starts to darken and become crispy 1–2 min (but not brown).  Season with salt and pepper, then transfer to a paper-towel-lined plate.

Cook prosciutto in same skillet over medium until crispy, 6–8 mins. Transfer frizzled prosciutto to a paper-towel-lined plate.

Serve risotto with crispy sage and frizzled prosciutto.