Heat olive oil in a large pot or deep skillet over medium heat.
Add the Italian sausage to the pot, 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.
Add the diced tomatoes with their juice, chicken broth, dried oregano, dried basil, crushed red pepper flakes, salt, and black pepper. Stir to combine.
Add the penne pasta to the pot and stir to submerge the pasta in the liquid.
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 12-15 minutes.
Remove the pot from heat and stir in the grated Parmesan cheese until melted and combined.
Sprinkle chopped fresh parsley over the top before serving.