Cook pasta to al dente as directed on package; set aside.
While pasta cooks, dice mushrooms, onion, and pepper. Heat olive oil in a large skillet over medium. Add mushrooms, onion and pepper. Season with oregano, basil, parsley, salt, and pepper. Cook and stir for 3-4 minutes, then add tomatoes. Stir in flour and cook for 2-3 minutes more; sauce will begin to thicken.
While sauce cooks, sauté shrimp in a separate skillet over medium heat; cook 3-4 minutes until pink. Toss shrimp into sauce and continue to cook 5 more minutes.
Top pasta with sauce, and serve with grapes on the side.