Mix grilled chicken breast, roasted garlic Alfredo sauce, grated parmesan, and mozzarella cheese together in a bowl and heat through on the stove until melted and warm.
Hollow out a French bread loaf, ensuring to leave enough crust to hold the filling without breaking.
Fill the hollowed loaf with the chicken Alfredo mixture, leaving some space at the ends to avoid overflow.
Top the filled bread with remaining grated parmesan and sprinkle with Italian seasoning.
Place the prepared bread on a baking sheet and bake in a 350°F oven for about 20-25 minutes until melty and golden.
Allow the bread to cool slightly before slicing and serving to avoid burns from the melted cheese.