Roughly cut peppers, onions, celery, and carrots. Add vegetables to large sauce pot with fresh sage leaves, bay leaves, 8 cups of water, and one tablespoon of salt. Cover and simmer for 2 hours. Remove from heat and cool.
Heat oven to 425 degrees. Peel squash and cut into cubes. Toss with olive oil and turn out on large baking sheet. Lightly salt and pepper. Roast until tender, about 50 minutes.
Remove the vegetables from the stock, leaving the carrots. Add the roasted squash to the broth and puree using an immersion blender. Cover and simmer for about 20 minutes. Salt and pepper as desired. Served with seasoned croutons.