Preheat oven to 400°F. Arrange the squash on a baking sheet and lightly dress with a drizzle of EVOO, salt and pepper. Roast for 35-45 minutes, until golden at edges and tender.
Meanwhile, bring a large pot of water to a boil and under-cook pasta by about 2 minutes, a little shy of al dente.
While the water comes to a boil, heat about 2 tablespoons EVOO, a couple of turns of the pan, over medium heat in sauté pan. Add garlic and stir a minute then add escarole and wilt. Season with a little salt and pepper, and add stock, simmer gently until ready to use.
In a small bowl, stir together ricotta, sage, salt, pepper and Parmigiano-Reggiano cheese.