Your roasting pan does most of the the heavy lifting here. Once the squash is tender making the soup is simply a matter of a quick whirl in a blender and heating up on the stove top.
You can roast the squash a few days in advance and keep it in the fridge for quick weekday soup making.
If you like, you can also add the flavour base to the blender when pureeing the soup for a totally smooth soup.
Blending the entire soup in the pot with an immersion blender also works well and will leave you with fewer dishes, however, the soup won't be quite as velvety as with an upright blender.
Leftovers can stored in the fridge for about 3 days, or be frozen in individual portions.