Preheat oven to 350 degrees F.

Cook lasagna noodles according to package directions until al dente.

Drain the cooked noodles and lay them flat on foil to cool.

Heat olive oil in a skillet over medium heat.

Add minced onion to the skillet and cook until tender, stirring frequently.

Stir in ready-cut Italian style tomatoes, tomato paste, and water.

Bring the mixture to a boil, then reduce heat to low and simmer for 5 minutes. Set aside.

In a bowl, combine ricotta cheese, thawed and drained minced spinach, 1/2 cup of shredded mozzarella cheese, slightly beaten egg, Parmesan cheese, salt, and black pepper.

Spread 3/4 cup of the tomato sauce mixture in the bottom of a 12x8-inch baking dish.

Spread about 1/3 cup of the cheese mixture onto each lasagna noodle, leaving a 1-inch border at the ends.

Roll up each noodle tightly.

Place the roll-ups seam-side down in the prepared baking dish.

Top with the remaining tomato sauce mixture.

Cover the dish with foil and bake for 35 minutes, or until heated through and bubbly.

Remove the foil and sprinkle with the remaining 1/2 cup of mozzarella cheese.

Continue baking until the cheese is melted and golden brown.

Serve hot.