Roasted Paleo Butternut Squash and Apple soup

3lb/1200g butternut squash (peeled and cubed)

Granny Smith apple (peeled, cored and cut into chunks)

yellow onion (chopped)

garlic (sliced)

fresh ginger (chopped)

Celery Stick (chopped)

olive oil

or 750mls, vegetable or chicken stock

sour cream to serve (optional)