Preheat oven to 400 F and line a large baking sheet with unbleached parchment paper.
To make the sauce, cut butternut squash in half lengthwise and remove seeds. Cut again in 4 pieces. Place on baking sheet cut side facing up. Add tomatoes and onions on the baking sheet.
Cut the top off the garlic bulb just enough to expose the garlic cloves and place full bulb on baking sheets.
Drizzle 3 tablespoons of olive oil all over vegetables and garlic. Season with 1/2 tsp salt and pepper and mix them to ensure they are covered well, Spread vegetables evenly on baking sheet with butternut squash cut side facing down. Roast in oven for 45-55 minutes until squash is fork tender.
Place squash, tomatoes, and onions in a food processor or high speed blender. Remove garlic from skin and add to processor with 1/4 cup olive oil. Blend until a creamy sauce. This makes 4 cups of sauce.
To make soup, heat a large dutch oven over medium heat. Add sausage and cook until golden and cooked through, about 6-7 minutes.
Add in bouillon cube and stir until melted. Stir in beans and add in butternut squash sauce and water. stir and bring to a boil. Reduce heat to simmer.
Add in spinach and season with salt and pepper. Simmer for an additional 10 mins. Feel free to add a bit more water to your preferred consistency.
Transfer to soup bowls and garnish with olive oil and chilies. Serve with rusk croutons.