Drizzle squash, onions, peppers, and garlic with olive oil and toss til coated. Sprinkle with Tony's and roast at 425 for 45 minutes to an hour until tender and slightly carmelized, but not burnt.
Add salt and pepper to carrots and celery in 4 cups water, bring to a boil, reduce to simmer and simmer until tender, 20 to 30 minutes.
Combine the two and blend with an immersion blender or carefully in a blender.(If you use a blender, start on low with lid on, do not overfill, cover with a cloth and blend slowly in batches).
If your bisque is not as thick as you like, you may thicken with a little cornstarch at this point, added to your half and half. Start with half of your half and half with some cornstarch. Then if you want to add more, you can.
You probably won't need any. It is entirely to the thickness that you desire.
If you want your bisque thinner, add more milk or extra broth and adjust it to the thickness you like.
Adjust seasonings. Add salt and pepper to taste. Cayenne pepper if desired.