Heat olive oil in a large pot or deep skillet 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 to the pot 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 juices and the chicken broth.
Add the penne pasta, dried oregano, dried basil, red pepper flakes, salt, and black pepper.
Bring the mixture to a boil, then reduce heat to medium-low and simmer uncovered, stirring occasionally, until the pasta is tender and most of the liquid is absorbed, about 15 minutes.
Remove the pot from heat and stir in the grated Parmesan cheese until melted and combined.
Garnish with chopped fresh parsley before serving.