Preheat the oven to 375°F (190°C).
Place each chicken breast between two pieces of plastic wrap and gently pound with a meat mallet or rolling pin until about 1/4 inch thick.
In a medium bowl, mix together the cream cheese, chopped spinach, sun-dried tomatoes, and shredded mozzarella cheese until well combined.
Season both sides of each flattened chicken breast with garlic powder, dried Italian seasoning, salt, and black pepper.
Divide the cream cheese mixture evenly among the chicken breasts, spreading it over one side of each breast.
Carefully roll up each chicken breast tightly, securing with toothpicks if needed.
Heat the olive oil in an oven-safe skillet over medium-high heat.
Add the chicken roll ups seam side down and sear for 2-3 minutes until golden brown.
Turn the roll ups to brown on all sides, about 2 minutes per side.
Transfer the skillet to the preheated oven and bake for 15-20 minutes, or until the chicken is cooked through and juices run clear (internal temperature should reach 165°F or 74°C).
Remove the toothpicks before serving. Let the roll ups rest for 5 minutes, then slice and serve.