Get a large pot of water on the stove to boil for the lasagna and salt it generously. While it comes to a boil, prepare the chicken filling. In a large cast iron skillet heat the olive oil over medium high heat. Add the diced chicken and let it cook through for about 5 minutes, then add the grape tomatoes, onion, garlic, rosemary, a pinch of salt, the pinch of crushed red pepper and dried oregano. Let the veggies soften for a minute with the chicken and then deglaze the pan with the white wine. Let the wine cook off for a couple of minutes. Take the pan off of the heat and stir in the spinach to let it gently wilt into the mixture. Set the mixture aside to cool for a couple of minutes.

Cook the lasagna in the boiling water for about 8-10 minutes, until it is tender. While the lasagna cooks, stir the ricotta, egg, nutmeg, cooled chicken mixture and a big pinch of salt together thoroughly in a big bowl to finish the filling. Take a large lasagna pan and lightly grease the bottom with a little of the bechamel sauce.

The lasagna noodles should be about done at this point, drain them and quickly separate them before they start to stick together. Lay them out on a clean work surface. Evenly spread a 1/4 cup of the chicken florentine filling along the length of each noodle, then roll them up tight and place them seam side down in the prepared lasagna pan. Pour the rest of the bechamel sauce evenly over the top of each noodle, then sprinkle a generous top layer of the freshly grated asiago cheese.

At this point, the tray of lasagna rolls can be covered and refrigerated overnight for an easy make ahead meal. When it is about time to serve, get the tray into a 350 oven to bake for about 25-30 minutes to let it bubble and heat through completely. Take it out when it's done, let it cool for a minute, and then serve immediately!