Roasted Sweet Potato and Apple Soup

My good friend Amy posted this on her blog, it comes from Real Simple magazine. I haven't tried it yet, but I'm intrigued enough by the idea of sweet potatoes in soup that I just *might* try it (they've got to taste better in soup form with apples than their natural, plain state, right?). She said it was divine! Let me know if anyone else tries it... Mom?

Roasted Sweet Potato and Apple Soup

3lb. sweet potatoes
1 Tbsp. olive oil
1 onion, chopped
1 celery stalk, sliced
1 Granny Smith apple, peeled and thinly sliced
salt and pepper

Heat oven to 400 degrees. Prick potatoes with a fork, place on baking sheet & roast until tender, 40 to 45 minutes. Meanwhile, heat the oil in a large sauce pan over medium-high heat. Add the onion, celery and apple and cook, stirring occasionally, until soft, 10 -12 minutes. When potatoes are done, halve them and scoop out the flesh and add to saucepan. Add 6 cups of water, 2 tsp. salt & 1/2 tsp. pepper. Cook until heated through, 8 - 10 minutes. Puree the soup in the saucepan using hand held blender, or pour small amounts one at a time in blender and blend. Add water if necessary to make desired consistency. Serves 8 (I halved the recipe and it still made plenty!)