Poke holes in squash with knife and roast in oven for 30-45 minutes until skin can be punctured with fork.
While squash is roasting, saute onion over medium heat until transparent. Add garlic and ginger, sauteing for another three minutes. Add carrots, celery, broth, water, salt, and pepper, and simmer on medium heath until vegetables are soft.
Remove squash from oven. Remove seeds and cut remainder into large pieces. Add to simmering pot.
Simmer for another 20 minutes.
Using an immersion blender. Blend all ingredients together until smooth.