Cook spaghetti according to package instructions. Drain and set aside. Reserve 1/2 cup pasta water.
Meanwhile, heat oil in a large skillet. Add shrimp and cook until no longer pink (about 7-8 mins). Add pepper, garlic and can of diced tomatoes. Season with salt, pepper and red pepper flakes. Cook for an additional 3-5 minutes to soften the peppers and allow the flavors to mingle. Add reserved pasta water, give it a stir.
Add pasta to shrimp skillet. Fold to combine. Garnish with fresh parsley and serve