Prepare the Meatballs:
In a mixing bowl, combine the torn bread with all of the lemon juice and half of the lemon zest. Allow the bread to absorb the liquid, then mash it until finely broken down.
Add the ground chicken and egg to the bowl, followed by the soaked bread.
Season with rosemary, minced garlic, basil, oregano, crushed red pepper flakes, black pepper, Parmesan cheese, and salt.
Thoroughly mix all ingredients until well combined.
Form the mixture into 1-ounce meatballs and roll them to tighten.
Place the meatballs on a parchment-lined baking sheet.
Roast in a preheated oven at 350°F (175°C) for 30 minutes, or until golden brown and cooked through.
Make the Soup:
Heat a large pot or Dutch oven over medium-low heat and dry-sauté the celery and carrots until they begin to develop a light color.
Add the chopped beet stems and minced garlic to the pot and sauté until the garlic becomes fragrant.
Pour in the chicken bone broth and bring to a boil, then reduce to a simmer.
Stir in the remaining lemon zest, basil, and oregano. Season with salt and pepper to taste.
Allow the soup to simmer for 20 minutes, or until the celery and carrots are tender.
Add the rotini pasta to the simmering broth and cook according to the package directions until al dente.
Remove the soup from the heat and gently add the cooked chicken meatballs.
Let the soup sit for 10 minutes to allow the flavors to meld.
Adjust the seasoning with additional salt, pepper, crushed red pepper flakes, and Parmesan cheese to your preference before serving.