Preheat oven at 425º. In a cookie sheet place 4 leg quarters, salt and pepper and place in the hot oven to start cooking. Cook until nicely roasted, 40 minutes
Dice all the vegetables into 1 to 1 ½ inch cubes. Place all the cut vegetables in a single layer on a large cookie sheet pan. Drizzle them with olive oil, thyme, salt and pepper. Toss well and bake for 25 minutes, or until the vegetables are tender, turning one with a spatula.
In a large saucepan heat 6 cups of chicken stock. When the vegetables are done roasting, puree them in a food processor. Add the puree to the soup. Scrape any oil that is remaining in the cookie sheet and added to the soup. Rectify the seasoning with salt and pepper to your liking.
Serve in a large soup bowl. Cut the chicken in small bite pieces and place in the middle of the soup. Serve nice and hot.