Preheat your oven to 350℉
Start the pot of boiling water, I recommend a large one so the noodles fit in all the way
Once boiling, cook the pasta until it is al dente, but soft enough to roll (it will cook a bit more in the oven)
Stir together ricotta, parmesan, egg, and salt & pepper
Defrost the spinach and completely drain, then add it into the cheese mixture
Once the pasta is done cooking, drain it and lay it out flat to dry a bit
Start spooning the cheese and spinach mixture onto the noodles and spread out evenly, then roll them up!
Lay some tomato sauce at the bottom of your baking dish, and place the rolled lasagna on the bottom
Pour the rest of the sauce over the rolls, and top evenly with some shredded or fresh mozzarella (fresh is better, but if you're like me and live in the NYC, it's way more expensive than it should be)
Bake about 30 minutes covered with tin foil, and remove for the last 10 minutes to make sure the cheese is melted