This 1206 model from GOOGLE SEARCH has what looks like a 13,500BTU Air Conditioner installed on its roof...
When I got my Starcraft 14RT trailer I had my AC installed by the dealer which they did in a few hours. They also included support bars across the interior ceiling to help support the extra weight on the roof like shown in this GOOGLE PHOTO.
The 120VAC Wiring on my roof mounted A/C is run in wiremode cable protector across the ceiling side and then down to the end of the ceiling where the tent bed end is installed and comes down inside a sewed in path of the window fabric. The 120VAC is then plugged into a 120VAC 20AMP receptacle mounted inside my wrap around seating storage cabinet. You will have to plug this in everytime you setup to power up your roof mounted A/C unit.
NOTE: this GOOGLE PHOTO shows a different way of plugging in the roof mounted air conditioner than how mine is installed. Most all of my wire is non-visible and behind the VALANCE curtain strip that goes around my whole interior roof area.
My roof raise is 12VDC Electric Motor controlled and operates just fine going up and down with the added weight. Have not had any problems with the up/down raise of the roof since purchased in 2008.
Unless you are really handy I would let the a dealer shop install the roof mounted air conditioner in the roof. It will require a 14x14-inch hole cutout in the roof. Some trailers may have the roof prepped for A/C Install already. They had to cut my 14X14-inch hole when mine was installed.
My 13,500 BTU Air Conditioner controls are all mounted on the bottom section of AC unit.
While the dealer is doing this install you might as well have them cut another 14x14-inch hole on the POPUP roof to install a roof mounted FAN-TASTIC VENT FAN if you don't already have one. Mine came with one already mounted and this really works well pulling in fresh air from a couple of cracked open window flaps. We couldn't do without our fan-tastic fan unit.