Preheat the oven to 375°F.
Line a baking dish with foil or grease lightly.
Flatten the chicken by placing the pieces between several sheets of plastic wrap. Use a meat tenderizer to pound until they are approximately ¼-inch in thickness.
Season both sides with salt and pepper.
Spread a thin layer of Dijon mustard over each piece of chicken.
Layer the spinach, roasted red peppers, and mozzarella on top of the mustard.
Roll up the chicken tightly, securing with toothpicks or twine.
Heat the olive oil in a skillet over medium heat.
Add the chicken rolls and sear each for 2–3 minutes per side, until golden brown.
Transfer the chicken rolls to the prepared baking dish.
Sprinkle with Italian seasoning.
Bake for 20–25 minutes or until the internal temperature reaches 165°F.
Let rest for 5 minutes before slicing.
Serve warm with your favorite side dish.