Easy Olive and Mushroom Pasta Saute

Name: Easy Olive and Mushroom Pasta Saute
Ingredients: 3 -4 tablespoons olive oil (of coarse what else lol!); 1 onion, chopped; 1 -2 tablespoon chopped fresh garlic; 1 -2 tablespoon dried oregano; 1 teaspoon dried red pepper flakes (or to taste); 2 (16 ounce) cans diced tomatoes, with juice; 5 ounces pitted black olives, sliced (or to taste, about 1 cup and a little more); 5 ounces pitted green olives, sliced (or to taste, about 1 cup and a little more); 12 ounces small shell pasta (cooked to firm-tender and drained); 1 -2 cup canned drained mushroom (or to taste); 3⁄4-1 cup grated parmesan cheese; salt and pepper