Preheat your oven to 375°F (190°C). Gather all your ingredients and equipment.

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

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

On parchment paper, flatten the meat mixture into a rectangle about ½ inch thick. Spread the cheese filling evenly over it, then roll it up tightly.

Place the rolled meatloaf seam-side down on a baking sheet and bake for 45-50 minutes, until the internal temperature reaches 160°F (71°C).

In the last 10 minutes of baking, cover the meatloaf with marinara sauce and return it to the oven.

Let the meatloaf rest for 10 minutes before slicing and serving with additional marinara sauce.