open coop design question

[tmoney438]

so far here is my coop. There is a roost on the back wall that you cant really see in the picture. first off keep in mind that I have been raising meat bird for the past couple of years and this is my first attempt at starting my laying flock. My original idea was to enclose the back top portion for the hens at night. I am considering not enclosing the back portion. I am wondering if I go ahead and finish roofing the whole coop do I need to enclose any portion for them? what are the benefits of enclosing the coop? I do still need to attach nesting boxes off the back so that I have access to them from the outside. I am trying to limit the weight so that I can pull them around the yard, but they will most days be free ranging while I am home to watch for predators. also I live in louisiana so I am much more concerned with heat than cold. thanks in advance for any feedback you guys can give me!