Preheat oven to 350F
Cut the butternut squash in half and brush 2 tablespoons of olive oil over the flesh part (not the skin).
Roast the butternut squash for 25-40 minutes, until slightly browned and an inserted skewer goes through the squash with little effort.
Scoop the butternut squash out of the skin and place in a large bowl.
Heat the remaining olive oil in a large stockpot over medium heat.
Add the garlic, onion and herbs.
Saute until the onion is translucent, then add 1 1/2 cups of the squash and stir well.
Thin the solution out with broth and allow it to come to a boil.
Meanwhile, cook the spaghetti according to package directions.
Use an immersion blender to puree the butternut squash mixture.
Stir in the cooked & drained spaghetti and stir to coat with the butternut squash sauce.
Serve hot.