The house I moved into had the patio converted into a sun room, the roof was nearly flat with less than 3/16" per foot of pitch. The roof was a torch down roll comp with the huge masonry fireplace right at the transisition. Time, moisture and gravity killed the pitch, then an additional layer of torch down was improperly applied at a later date. What a mess.
During the repair to a pitch suitable for standing seam metal roof, we had a downpour. All the drywall in the sun room was toast, along with insulation. Actually, sogged and sagging. That was quite the mess, three trailers full of crap for the dump. We waited until the new roof was proven before the rest of the repair.
First, the door was removed and relocated to a central location. A commercial French door 7'-11" tall was installed. The room was rewired for switch access and half dozen cans installed for recessed lighting. Then insulation and drywall. Fun stuff on the ceilings. But a drywall jack made that easier, if not a marriage test. My new impact driver with the drywall bit worked like a champ. One charge for 14 sheets. Ryobi.
Now it is tape and floating. Fortunately, I have a mini scaffold which makes working on these 10' ceilings easier. Half done there, walls will take no time. Two windows to corner bead too.