If you have Yakima RackandRoll trailer the tent should not be used on it. The tent will sit lower than the minimum required height for the ladder of 45" from the crossbar to the ground. The reason this is important is that the ladder provides support and stability to the tent.
For other trailers, use of the tent would fall under a Custom installation please contact the manufacturer for their recommendation and options for carrying roof top tents. Also refer to our "Best Practices" pdf attached below.
Still can't find what you are looking for, no problem you can contact Support here, or by calling 888-925-4621 M-F from 7 to 4 PT.