Preheat oven to 425 degrees F. Spray a 9 x 13-inch baking dish with cooking spray.
Stir marinara sauce, tomatoes (in their juice), and uncooked rice together in the prepared dish (or in a separate bowl).
In a small bowl, combine diced, uncooked chicken with Italian seasoning and salt.
Add seasoned chicken to the rice mixture and stir to completely combine. Transfer to prepared baking dish.
Cover tightly with foil or with a lid.
Bake for 35 minutes, remove the cover, and give the dish a good stir. At this point the chicken should be cooked through and the rice should be just about tender (but still slightly al dente). If the rice is too hard, cover the dish and return to the oven for 5-10 more minutes, or until it’s ready.
Once the rice is just about tender, sprinkle mozzarella and Parmesan cheeses over top. Return dish to the oven, uncovered, for about 5 more minutes, or just until cheese is melted and rice is completely done.
Garnish with parsley before serving.