Preheat the oven to 350°F (175°C).
Cook the lasagna noodles in a large pot of salted boiling water according to package directions until al dente; drain and lay noodles flat on wax paper or a sheet to cool and prevent sticking.
Steam the spinach until wilted (or sauté briefly); squeeze out excess liquid and finely chop.
In a medium bowl, stir together the ricotta, chopped spinach, eggs, Parmesan, garlic powder, salt, pepper, and 1 cup of the shredded mozzarella until evenly combined.
Spoon 1 cup of marinara sauce into the bottom of a 9 x 13 baking dish and spread into an even layer.
Spread about 1/4-inch of the ricotta mixture evenly over each cooled noodle, then gently roll up each noodle and place seam-side down in the prepared baking dish.
Spoon remaining marinara sauce over the rolls and sprinkle with the remaining 1/2 cup of shredded mozzarella (or remaining portion of the 1 1/2 cups).
Bake, uncovered, for 35–40 minutes until the cheese is melted and bubbly and the sauce is hot; remove and let rest a few minutes before serving.