Bring a large pot of salted water to a boil. Cook the Gemelli pasta until al dente, according to package directions. Reserve 1 cup of pasta water, then drain the rest. Set the drained pasta and pasta water aside.
To a large skillet over medium heat, add oil. Once hot and shimmering, add the smoked sausage in a single layer. (Depending on the size of your skillet, you may need to work in batches.) Sear for 2-3 minutes per side, or until browned and crisp. Transfer the sausage to a plate and set aside.
To the same skillet (don't drain the oil), sprinkle in the flour. Whisk, scraping up any brown bits, until a paste forms and the mixture starts to brown.
Slowly whisk in the milk. Whisk continuously until the mixture thickens slightly, about 5 minutes.
Stir in the chicken broth, Cajun seasoning, garlic powder, and salt. Bring to a light simmer.
Add the corn and Parmesan. Stir and let simmer for 5 more minutes.
Return the pasta and sausage to the skillet, stirring to combine. If the sauce is too thick, stir in a bit of the reserved pasta water,1 tablespoon at a time, until the desired consistency is reached.
Garnish with parsley and more Parmesan before serving