CUT squash into quarters. Scoop out and discard seeds. Roast pieces in a large baking dish covered with foil, until fork-tender, about 1 hour. Remove from oven. (Reserve some squash to garnish, if desired.) When cool enough to handle, scoop flesh from skins. Whirl in a food processor until smooth. (Purée refrigerates for up to 3 days.)
HEAT a large saucepan over medium. Add olive oil, garlic and 1 cup squash purée. Cook for 1 min.
POUR in vegetable broth and 10% cream. Boil, then stir in macaroni pasta. Reduce heat to medium-low and cook, stirring often, until pasta is tender, 6 to 8 min.
STIR in parmesan. Top with roasted butternut squash pieces, if desired.