1. Combine all filling ingredients. To stuff each crepe, place a line of filling along one side of a crepe and roll up. Place in baking pan. Repeat with remaining crepes and filling.
2. Prepare the white sauce. Melt butter in a saucepan. Whisk in flour, then add milk and whisk. Cook until sauce thickens to the same consistency as marinara, stirring just occasionally. Season with salt. Pour sauce over crepes in baking pan.
3. Top with shredded mozzarella. Bake until cheese is melted, golden, and bubbly and edges of some crepes are crispy about 30 minutes.