Bring a large pot of salted water to a boil and cook the gemelli according to package instructions until al dente. Reserve ½ cup of pasta water, then drain and set aside.
Meanwhile, heat the olive oil in a large skillet over medium heat. Add the onion and cook for 3 to 4 minutes until softened.
Stir in the garlic, sun-dried tomatoes, Italian seasoning, and red pepper flakes. Cook for 1 minute until fragrant.
Pour in the vegetable broth and oat cream. Bring to a gentle simmer and cook for 2 to 3 minutes, stirring occasionally.
Add the vegan parmesan and stir until melted and combined. Stir in the spinach and cook until wilted, about 1 to 2 minutes.
Add the cooked pasta to the skillet and toss until evenly coated in the sauce. If needed, stir in a splash of reserved pasta water until the sauce reaches your desired consistency.
Season with salt and black pepper to taste. Serve warm with extra vegan parmesan on top.