Heat the butter on low heat. Add the flour and stir well until the flour and butter are completely mixed. Pour the milk slowly, while you stir the flour mix to prevent lumps. Once it is well mixed, boil on low heat until the mix thickens to the same consistency as drinkable yogurt.
Season with salt and pepper to taste. Remove from heat and stir until it cools down to room temperature. Mix with 1 cup of parmesan and set the sauce and remaining parmesan to the side for later.
To make the filling
Heat the oil on very low. Add the onions and cover with a tight lid. Cook on low heat until the onions become transparent. Add the turkey and increase the heat to low, stirring frequently until the turkey heats up. Add the tomato sauce and cook on low until warm. Season with salt and pepper to taste. Let it cool to room temperature.
To make the rolls
Preheat the oven to 400 ºF [200 ºC].
Boil the lasagna according to package directions.
Spread ⅛ of the meat evenly over each lasagna noodle and roll it up.
Spread half of the white sauce in a baking dish and place the lasagna rolls in the dish with the seam facing down. Cover the rolls with the remaining sauce.
Cover the dish with foil.
Bake until the sauce starts to bubble (around 20 minutes). Remove from the oven, sprinkle with the remaining parmesan and the chopped parsley.
Serve hot and with salad.
For a low-carb option, use thin slices of zucchini in lieu of lasagna noodles. And Pour yourself an extra glass of milk to add some more nutrients to your meal.