Cook rotini in salted water according to package directions until al dente. Drain, rinse with cold water, and set aside.
Season chicken breasts with Montreal Chicken seasoning and cook through by your preferred method. Rest 5 minutes, then dice into 3/4-inch cubes.
In a large skillet over medium heat, whisk together Alfredo sauce and milk until combined.
Add Italian seasoning, salt, and pepper. Simmer gently for about 5 minutes, stirring occasionally.
Add cooked rotini and diced chicken to the sauce. Toss to coat.
Cook on low for about 10 minutes, stirring occasionally, so the pasta absorbs some sauce.
Add shredded mozzarella and stir until melted through. Serve immediately.
Notes
Rinse the pasta after cooking so it does not clump before going into the cream sauce. Use Montreal Chicken seasoning generously so the chicken tastes seasoned. Keep the sauce at a gentle simmer and low heat after adding pasta. Do not use fresh mozzarella because it can make the sauce watery.