In a large deep skillet or Dutch oven over medium heat, crumble and cook the Italian sausage until browned and cooked through, about 5-7 minutes. Use a slotted spoon to transfer sausage to a plate and set aside, leaving the rendered fat in the pot.
Add the diced onion to the pot and sauté in the sausage fat until softened and translucent, about 3-4 minutes.
Stir in the minced garlic and cook for 30 seconds until fragrant.
Pour in the diced tomatoes with their juice, chicken broth, and water. Stir to combine.
Add the penne pasta, dried oregano, dried basil, crushed red pepper flakes, salt, and black pepper. Stir well to combine all ingredients.
Bring the mixture to a boil, then reduce heat to medium-low. Cover and simmer, stirring occasionally, until the pasta is tender and most of the liquid is absorbed, about 15 minutes.
Return the cooked Italian sausage to the pot and stir to combine. Cook uncovered for 2-3 minutes to heat through and thicken the sauce slightly.
Remove from heat and stir in the grated Parmesan cheese until melted and combined.
Garnish with chopped fresh parsley before serving.