As anyone who has been to Italy or to one of our good Italian restaurants knows, there is more than one way to dress pasta. And there is more than one role it plays in a meal.

Italians have traditionally eaten pasta as a separate course preceding the main one. But in the United States spaghetti, noodles, macaroni shells or any of their cousins have worked their way into main courses and salads.

Simply dressed with a sprinkling of grated cheese, spaghetti or fettucine are nice companions to all kinds of grilled meats. A sauce of sauteed green pepper, cream and smoked salmon turns freshly made fettucine into an elegant first course. Or pasta with a spicy tuna and tomato sauce can, with an accompanying salad, constitute a meal in itself. Here are three delicious and different ways of preparing pasta. The yield from each recipe is calculated in small portions. If you like them large, increase the recipes by 50 percent. SPAGHETTI RIGOLETTO (3 servings)

A friend was generous enough to share this unlikely recipe with me. Her husband, an avid opera fan and cook, says it came from Luciano Pavarotti himself.It makes a zesty first course or the basis of a light lunch or dinner. The original version came as a list of unmeasured ingredients. Measurements are my own and can be varied to suit your taste, particularly to tone down or increase the pepper. 1/2 pound spaghetti 3 ounces tomato paste 4 tablespoons quality olive oil 1 clove of garlic, crushed 1/4 teaspoon red pepper flakes 1/4 cup minced parsley

While the spaghetti is boiling, mix the other ingredients together. When the pasta is cooked al dente, drain. Toss the hot spaghetti with the sauce. It may served with grated cheese. GREEN PEPPER AND SMOKED SALMON SAUCE (4 servings)

This rich sauce has the finesse to make it an ideal first course at a dinner party. It deserves good, freshly made fettucine but can also be used with a high-quality dried product. 6 tablespoons best quality olive oil 1 large green pepper, seeded and diced 1 1/2 cups heavy cream or more 1/4 pound smoked salmon Salt and pepper to taste 3/4 to 1 pound fettucine or other noodles

Saute the green pepper in the olive oil over medium heat, stirring occasionally, until the pepper begins to soften and darken, about 5 minutes. Add the cream and simmer, stirring, until the cream thickens slightly and blends with the olive oil. Remove from the heat. Slice the smoked salmon into ribbons about 1/2-by-1 1/2 inches and reserve. Cook the fettucine.

A few minutes before the fettucine is ready, heat the cream to just below simmering. If it has reduced to less than 3/4 cup, add more cream to thin it out. Add salt and pepper to taste. As soon as the pasta is ready, drain it and toss with the cream and green pepper mixture. Strew the smoked salmon over the pasta and toss again. Do not serve grated cheese with this dish. SPICY TUNA AND TOMATO SAUCE (2 servings as main course, 3 to 4 servings as first course)

This really is a dish for summer, when the tomatoes are at their best and the basil is flowering in the garden. The winter version, with dried herbs and canned tomatoes, has a mellower character than the spirited summer version. 1 large onion 3 tablespoons olive oil 1-inch piece green chile, minced Few sprigs fresh thyme or 1/2 teaspoon dried Handful fresh basil leaves or 1 teaspoon dried 2 large fresh tomatoes or, in water, 3 to 4 good-quality canned tomatoes 1 clove of garlic, crushed 3 1/2- to 4-ounce can oil-packed light tuna Salt and pepper to taste 1/2 pound pasta

Dice the onion and saute slowly in the olive oil until it becomes soft and translucent. Add the green chile, the leaves from the sprigs of thyme (or the dried thyme) and the basil, chopped (or the dried). Dice the tomatoes and add them to the pan. Cook slowly until the tomato softens. Add the well-crushed garlic and the tuna. Season to taste with salt and pepper. Cook slowly until the tuna becomes soft. Serve over hot pasta. Pass grated cheese separately.

NOTE: Pasta is often served with grated cheese. Imported parmesan at $9 per pound has priced itself out of everyday use in my kitchen. Good substitutes at half the price come from Argentina. I have bought them under the generic names of sardo, regiano and Argentine parmesan.