Though your experience probably covers this, here is the info Peter referenced:
"ROOF RACKS AND LOAD CARRIERS (IF EQUIPPED) WARNING: When loading the roof racks, we recommend you evenly distribute the load, as well as maintain a low center of gravity. Loaded vehicles, with higher centers of gravity, may handle differently than unloaded vehicles. Take extra precautions, such as slower speeds and increased stopping distance, when driving a heavily loaded vehicle. Note: The maximum recommended load, evenly distributed on the crossbars, is 100 pounds (45 kilograms). Note: Never place loads directly on the roof panel. The roof panel is not designed to directly carry a load. Load Carrying 269 2014 Explorer (exp) Owners Guide gf, 3rd Printing, September 2013 USA (fus) For correct roof rack system function, you must place loads directly on crossbars affixed to the roof rack side rails. We recommend you use Ford Genuine Accessory crossbars designed specifically for your vehicle. Make sure that you securely fasten the load. Check the tightness of the load before driving and at each fuel stop. Adjusting the Crossbars (If Equipped) Note: Wind noise can be minimized by either removing or repositioning the crossbars when they are not is use. Position the rear crossbar fully rearward and the front crossbar 10 inches (25 centimeters) from the front end-cap. 1. Loosen the tie-down hooks at both sides of the crossbar by turning them counterclockwise. A small screwdriver or similar tool can be used to break the torque by inserting the shaft into the tie-down hook and twisting. 2. Slide the crossbar to the desired position. This may require someone on each side of the crossbar. 3. Tighten the tie-down hooks at both sides of the crossbar by turning them clockwise until tight. A small screwdriver or similar tool can be used to tighten the hook an additional half turn. Make sure to check that the tie-down hooks are tight each time a load is added or removed from the roof rack, and periodically while traveling. Make sure that the load is secure before traveling."
That tent looks nice, and looks like it is completely clear of the roof surface so I doubt the sunroof matters. Someone can correct me if I am wrong, and my advice is only my opinion so don't take it as legal counsel, all that typical language saying I am NOT AN EXPERT! The roof structure is designed to withstand roll-over/roof crushing forces regardless of the presence of a sun roof. The roof rack should tie directly to that support structure, not the flimsy roof skin, and should therefore support significant loads. That's what I think ,anyway. Rovers have had open roofs and Jeeps have soft tops, both have had countless people sleeping on top of them... The manufacturer even shows it on soft-top vehicles...
Something else you may like, btw:
http://pronghorngear.com/linktrac/
Cheers