Preheat oven to 450 degrees. Roast squash in the oven for 50 minutes (depends on how big or what kind of squash you have) or until tender when pierced with a fork. Set aside to cool.
While the squash is cooling, saute the onion, celery, and garlic in melted butter on medium heat until onion is translucent, about 5-6 minutes. Turn down heat to low and add flour constantly stirring for a minute or two to cook the roux. Add cold stock and brandy. Turn the heat up to medium /medium high stirring occasionally and bring to a boil.
While the stock comes to boil, scoop out the flesh from the squash and add to the stock. Add chopped sage and rosemary to mixture. When the stock is at a boil reduce the heat and simmer 5-10 minutes. Finish with the cream and herbs. Blend the soup to a nice, smooth consistency with immersion blender or in food processor. Transfer back to pot and cook for another couple minutes.
Serve soup garnished with croutons or crusty bread. Enjoy!