Bring a large pot of water to a boil. Season generously with salt. Add rigatoni and cook until al dente according to package directions. Drain; return to pot and cover.

Heat a large skillet over medium-high heat. Add sausage. Cook until well browned on both sides, about 5 minutes. Remove sausage to a bowl;set aside.

Reduce heat to medium. Add butter to the same skillet. Once butter is melted, add flour and whisk to combine. Cook for 1 minute. Slowly pour in milk while whisking to prevent any lumps from forming. Bring sauce to a simmer, whisking often. Once bubbling, add cheese. Stir until cheese is melted. Season with salt and pepper to taste.

Pour sauce over cooked pasta, add kielbasa and half the apples. Stir to combine. Portion pasta, and top with remaining apples - distributing evenly among the dishes. Serve immediately.