Heat olive oil in a large deep skillet or Dutch oven over medium heat.
Add the Italian sausage, breaking it up with a spoon, and cook until browned and cooked through, about 5-7 minutes.
Add the diced onion and cook until softened, about 3 minutes.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the diced tomatoes with their juice, chicken broth, penne pasta, dried oregano, dried basil, and crushed red pepper flakes.
Stir to combine and bring the mixture to a boil.
Reduce heat to medium-low and simmer uncovered, stirring occasionally, until the pasta is tender and most of the liquid is absorbed, about 12-15 minutes.
Season with salt and freshly ground black pepper to taste.
Remove from heat and stir in the grated Parmesan cheese until melted and well combined.
Garnish with chopped fresh parsley before serving.