Cook the pasta according to the package directions JUST until al dente. Immediately strain the pasta. Run it under cold water, stirring to stop the pasta from cooking further.
In a large heavy bottomed pot, melt the butter over medium heat. As soon as it's melted add the flour, whisking to combine. Let the mixture bubble for 30 seconds to cook off any flour taste.
Raise the temperature to medium high and add in the milk 1/2 cup at a time, until all the milk's been incorporated and simmer, whisking often, until the roux has thickened.
Reduce the heat to medium low, and add the cheese- one cup at a time- whisking until all the cheese has been incorporated and the sauce is smooth.
Add the marinara sauce & tomato paste to the cheese sauce, whisking to evenly combine.
Add the pasta into the pot, and gently toss until all of the pasta is evenly combined & saucy. Season with salt & pepper, to taste.
Transfer the pasta mixture to a 9x13" baking dish that has been lightly sprayed with non-stick cooking spray.
Add the bread crumbs, Italian seasoning, and melted butter to a small mixing bowl. Stir together until evenly combined, and then spread them out evenly over top of the casserole.
Bake the macaroni & cheese at 350° for 20-25 minutes. Remove the casserole from the oven, serve, and enjoy!