Heat olive oil in a Dutch oven over medium heat. Add chopped onion, carrots, celery, and garlic clove; sauté 5 minutes. Sprinkle flour, oregano, thyme, and poultry seasoning over vegetables, and cook 1 minute. Stir in broth, potato, and salt. Bring to a boil; reduce heat, and simmer, partially covered, 25 minutes or until potato is tender. Add roasted chicken, milk, and noodles, and cook 10 minutes or until noodles are tender. Garnish with fresh thyme, if desired.