Place each chicken breast between two sheets of plastic wrap and pound them to about 1/4 inch thickness using a meat mallet or rolling pin.
In a mixing bowl, combine ricotta cheese, half of the mozzarella cheese, Parmesan cheese, chopped spinach, garlic powder, Italian seasoning, salt, and pepper. Mix until well combined.
Spread an equal amount of the cheese mixture onto each chicken breast, leaving a small border around the edges.
Carefully roll each chicken breast tightly and secure with toothpicks or kitchen twine.
In a large oven-safe skillet, heat olive oil over medium heat. Add the chicken rolls and sear them for about 3-4 minutes on each side until golden brown.
Pour marinara sauce over the chicken rolls in the skillet, then sprinkle the remaining mozzarella cheese on top.
Transfer the skillet to the preheated oven and bake for 25-30 minutes, or until the chicken is cooked through and the cheese is bubbly.
Remove from the oven and let it rest for 5 minutes before serving. Garnish with fresh basil leaves if desired.
Notes
For a spicier version, add crushed red pepper flakes to the cheese mixture.
Substitute the spinach with cooked and chopped mushrooms or roasted red peppers for a different flavor profile.