Preheat your oven to 375°F (190°C). Gather your baking dish and mixing bowls.

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

In a separate bowl, mix mozzarella cheese, Parmesan cheese, and spinach until evenly distributed.

Lay out the meat mixture on parchment paper, shape into a rectangle. Spread cheese filling, roll meat around it and pinch edges to seal.

Transfer to a greased baking dish and bake for 45-50 minutes until the internal temperature reaches 160°F (71°C).

Spoon marinara sauce over the meatloaf during the last 10 minutes of baking.

Let it rest for about 10 minutes before slicing. Serve with additional marinara sauce.