In a bowl, mix ground chicken, breadcrumbs, Parmesan, egg, garlic, rosemary, salt, and pepper until just combined. Form into 1 1/2-inch meatballs (about 16) and place on the baking sheet. Drizzle or brush with olive oil. Bake for 18–20 minutes or until golden and cooked through (internal temp 165°F).

While the meatballs bake, heat olive oil in a deep skillet over medium heat. Sauté onion for 2–3 minutes until soft, then add garlic and orzo and cook for 1–2 minutes until lightly toasted. Stir in diced tomatoes, chicken broth, salt, pepper, and red pepper flakes. Bring to a boil, then reduce heat and simmer uncovered for 10–12 minutes, stirring occasionally, until orzo is tender and the liquid is mostly absorbed.

Stir in herbs and adjust seasoning. Top the tomato orzo with warm rosemary chicken meatballs and garnish with grated Parmesan before serving.