Preheat oven to 400°. On a foil-lined baking sheet, toss squash with 1 tablespoon olive oil. Roast squash, stirring halfway through, until tender and starting to caramelize, 40 minutes. Transfer to a large bowl; roughly mash. Reduce heat to 350°., Cook pasta according to package directions. Drain., In a large nonstick skillet over medium-high heat, cook sausage and 1 cup onion, crumbling meat, until no longer pink. Add baby kale; cook until kale is tender, 3-5 minutes. Mix with squash. Stir in 4 ounces goat cheese., In same skillet, heat remaining olive oil. Add remaining onion; cook until softened, 3-5 minutes. Add garlic; cook, stirring, for 1 minute more. Add tomatoes, sage and sugar; bring to a boil. Reduce heat; simmer, stirring occasionally, until sauce is thickened, about 15 minutes. Cool about 5 minutes. Pulse in a blender until combined. Add half-and-half; pulse until smooth. Pour about half of sauce in a greased 13x9-in. baking dish., Stuff each shell with about 2 tablespoons squash mixture; arrange in the baking dish. Pour remaining tomato sauce over shells; top with remaining goat cheese. Bake, covered, until beginning to bubble, 20 minutes. Remove cover; bake another 10 minutes. Let stand 10 minutes before serving.