For the eggplant

Spray a stovetop grill pan with nonstick vegetable spray.  Heat the grill over medium/high heat.  Add the sliced eggplant to the grill and cook the eggplant, turning once, until grill lines appear on both sides.  

Repeat with the remaining eggplant slices.  Set aside.

For the filling

In a medium bowl combine the ricotta, mozzarella and parmesan cheeses.  Blend in the egg, onion, salt and black pepper.

To Roll

Spray a casserole with nonstick vegetable spray.  Set aside.

Preheat oven to 350° F.

Place an eggplant slice on a flat surface.  Evenly spread a portion of the filling over the eggplant.  

Starting at the narrow end, roll up the eggplant.  Place seam side down in the prepared casserole.

Repeat with the remaining grilled eggplant slices.

To finish

Top the eggplant rolls with the marinara sauce. Cover and bake for 30 minutes.

Uncover the rolls, top with the remaining mozzarella and bake for an additional 30 minutes until the cheese is melted, hot and bubbly.

Serve hot or cold.