Melt butter in a medium saucepan over medium heat. Add flour, paprika & Italian seasoning & stir until well incorporated. Slowly, add milk & whisk together until smooth. Continue whisking until sauce comes to a slow boil & starts to thicken. Stir 1/3 of the sauce into the sausage mixture. (Reserve the other two thirds to pour under & over the cannelloni.) Add 340 gm shredded mozzarella to the sausage & sauce mixture & mix to combine.