Preheat your oven to 375°F (190°C).

In a large bowl, combine the ground beef, Italian sausage, breadcrumbs, eggs, garlic powder, onion powder, Italian seasoning, salt, and pepper. Mix gently until just combined.

In a separate bowl, mix the mozzarella and Parmesan cheeses together. Optionally, add spinach.

Flatten the meat mixture into a rectangle. Spread the cheesy filling evenly, then roll it up, sealing the edges tightly.

Place the rolled meatloaf seam-side down onto a baking sheet or in a loaf pan. Bake for 45-50 minutes until the internal temperature reaches 160°F (71°C).

In the last 10 minutes of baking, spread marinara sauce over the top.

Let the meatloaf rest for about 10 minutes before slicing. Serve warm.