Preheat the oven to 350°F (175°C).
Slice the eggplants about 1/4-inch thick and arrange in a single layer on a baking sheet; brush both sides with olive oil and season with sea salt and black pepper.
Roast the eggplant in the preheated oven until tender and lightly browned, about 10 minutes.
Prepare the marinara sauce according to its recipe, adding cooked and drained ground beef if using.
In a mixing bowl, combine the ricotta, eggs, and grated Parmesan until smooth and well blended.
Lightly oil or spray a baking dish. Assemble the lasagna by layering: a thin layer of sauce on the bottom, half of the ricotta mixture, a layer of roasted eggplant, the remaining ricotta mixture, more sauce, and finish with the grated mozzarella on top.
Bake the assembled lasagna at 350°F (175°C) until bubbly and the cheese is melted, about 30 minutes. Let rest a few minutes before slicing and serving.
