Add sausage to a large pan and set over medium heat. Break up sausage into crumbles and cook, stirring occasionally, until fully cooked and no pink remains. Transfer cooked sausage to a paper towel-lined plate to absorb excess grease and wipe out pan to use again.
Set the now-empty pan over low-medium heat and pour in about 1/4 cup water. Add in as much spinach as can fit in the pan and cover, stirring everything up and adding more spinach as room frees up. Cook until spinach wilts, then transfer spinach to a colander lined with paper towels. Let spinach drain, then press out as much of the excess liquid as you can. Set aside for now.
Bring a large pot of salted water to a boil. Once boiling drizzle in 1-2 tablespoons of olive oil. Add lasagna noodles and boil according to package directions* (see note below).
Meanwhile spray two large baking sheets with cooking spray (mine are 13"x17" and fit 6 noodles on each). You may also use sprayed sheets of aluminum foil as your lasagna roll assembly surface. Once noodles are to your preferred doneness, drain and lay noodles in a single layer on greased baking sheet (or foil).
Add egg to a mixing bowl and whisk until light and creamy. Add cooked and crumbled sausage, spinach, ricotta, Pecorino Romano (or Parmesan), salt, and pepper and stir until everything is combined evenly.
Spray an 8"x10" (or similarly sized) baking dish with cooking spray and spread 3/4 cup of marinara sauce evenly on the bottom. Set aside. Preheat oven to 350°F.
Using a cookie scoop (or two spoons), add about 1/4 cup total of the ricotta mixture over top of each noodle in dollops. Spread the mixture into an even layer on each noodle,
Roll each noodle as tightly as you can (from the short side) without squishing the filling out of the sides and place each lasagna roll seam-side down in the baking dish. Place lasagna rolls close together in the pan to help keep them in place.
Once all rolls are in the dish, pour remaining marinara sauce evenly over top and top with mozzarella. Cover with aluminum foil, spraying the bottom side of the foil with cooking spray so it doesn't stick to the cheese.
Bake for 20 minutes, then remove foil and bake for another 20-25 minutes, or until bubbly and the cheese has melted. Top with chopped basil for serving.
Lasagna noodle cook time: I've noticed different brands of lasagna noodles specify slightly different boil times. I've used one that says 8 minutes, and another that says 10. Either way, I cook the noodles about 1 minute to 30 seconds less than the package indicates to ensure they're bendable but not mushy.Sausage varieties: You can use mild Italian sausage if you don't want this dish to be spicy. If you can only find mild sausage and like spicy things, add crushed red pepper flakes to the sauce in line with your tastes.You can also use ground turkey or chicken Italian sausage to lighten the nutritional stats, which take into account the use of pork sausage.Nutritional info: The information displayed is an estimate for two sausage rolls. Amounts will vary depending on the brand of ingredients you use.