Cut onions into quarters leaving the skins on. Cut ginger into one-inch pieces and chop the top part of the garlic bulb off, leaving the cloves intact. On a parchment paper lined cookie sheet, roast onions, ginger, and garlic for 30 minutes at 400F.
Remove approximately 2 cups worth of meat from a cooked rotisserie chicken. Set the shredded chicken aside. Reserve the chicken carcass for making the broth.
Cook rice noodles according to package and set aside.
Add roasted onions, ginger, and garlic to a large stock pot with the rotisserie chicken carcass. Cover completely with water, about 8-10 cups.
Stir in rosemary, thyme, fish sauce, hoisin sauce, cinnamon stick, lime, salt, and pepper.
Simmer on medium heat for 2-3 hours. Strain broth through a fine mesh sieve.
Add shredded chicken to the broth and serve in large bowls. Garnish with toppings of your choice.
