Preheat the oven to 400 degrees, and line a large baking sheet with parchment paper.
Form the mozzarella cheese into 8 evenly sized circles on the baking sheet. Be sure to leave a space between each cheese circle, as they will expand a bit when baking.
Add the ground sausage to a skillet over medium high heat, and saute until browned completely. Drain the excess fat.
Return the skillet to medium heat, and stir in the onion and garlic.
Saute until the onion softens.
Stir in the cream cheese until melted.
Add in the spinach, and saute until wilted.
Remove from the heat and allow to cool.
Place the cheese into the oven, and bake for 8 minutes, or until the edges start to brown.
Remove the cheese from the oven and let cool for a few minutes.
While the cheese is still hot, but able to be handled, place a layer of the filling in the center of each cheese circle.
Fold the cheese up around the filling to form rollups.
Let the rollups cool and become crispy before serving.