Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain and cool on waxed paper or aluminum foil to prevent the noodles from sticking together.
Preheat oven to 350 degrees F (175 degrees C).
In a medium bowl, combine ricotta cheese, mozzarella cheese, Parmesan cheese, parsley, salt and pepper; fill manicotti with cheese mixture.
In a 9x13 inch baking dish, spread a thin layer of spaghetti sauce on the bottom and arrange manicotti in a single layer; cover with remaining sauce. Cover dish with aluminum foil and bake in preheated oven for 40 minutes. Remove foil and bake for 15 minutes longer; serve.