Preheat your oven to 400°F (200°C).
Place the cubed butternut squash on a baking sheet and drizzle with olive oil. Toss to coat the squash evenly.
Roast the squash in the preheated oven for 30-35 minutes, or until it is tender and slightly caramelized.
In a large pot, heat a tablespoon of olive oil over medium heat. Add the chopped onion and minced garlic cloves. Sauté until the onion is translucent and fragrant.
Add the roasted butternut squash to the pot and stir to combine with the onion and garlic.
Pour in the vegetable broth, ground cinnamon, ground nutmeg, and ground ginger. Stir well to incorporate the spices.
Bring the mixture to a boil, then reduce the heat and let it simmer for 15-20 minutes to allow the flavors to meld together.
Using an immersion blender or a regular blender, puree the soup until smooth and creamy.
Return the soup to the pot and stir in the heavy cream. Season with salt and black pepper to taste.
Simmer the soup for an additional 5 minutes to heat through.
Serve the roasted butternut squash soup hot, garnished with a drizzle of cream, a sprinkle of ground cinnamon, and a few roasted squash seeds for added crunch.