Start this process during the second half of the vegetables roasting, when you have about 10 minutes left.
Add butter to a large dutch oven or stockpot (whatever you would normally cook a big batch of soup in), and heat over MED HIGH heat.
Once melted, add diced onion, diced carrot, and diced celery. Sprinkle with salt and pepper and stir.
Cook for 3-5 minutes, stirring occasionally, until vegetables are softened and lightly golden.
Stir in cinnamon, rosemary, sage and nutmeg.
Add roasted vegetables from the baking sheet, then pour in chicken broth.
Use an immersion blender to puree the soup until smooth or desired texture is reached.
Continue heating until hot throughout (this time will vary from person to person), mine just took about 5 minutes. Taste, and add salt and pepper if necessary.