Lay the butterflied flank steak flat on a clean surface and cover with plastic wrap. Pound to an even 1/2-inch thickness if needed.
Drizzle the olive oil over the steak, then season evenly with garlic powder, Italian seasoning, salt, and black pepper.
Sprinkle cheese evenly over the steak, leaving a small border around the edges. Add spinach and roasted red peppers if using.
Starting from one short end, roll the steak up tightly into a log. Secure with butcher’s twine at 1 to 2-inch intervals.
Preheat a skillet or grill over medium-high heat. Sear the pinwheel log for 2–3 minutes per side until nicely browned.
Transfer to a 375°F (190°C) oven and bake for 15–20 minutes, or until the internal temperature reaches 135°F (medium rare) to 145°F (medium).
Let rest for 5–10 minutes, then slice into 1-inch pinwheels. Serve warm and enjoy!