Set up an A-frame ladder that has a height tall enough for you to climb to the top and have your arms a couple feet higher than the trailer's roof. Place the ladder so that the rungs run parallel to the length of the trailer and the starting point is at one end of the trailer. Position the ladder so that it is about 5 feet away from the rooftop.
Climb the ladder, holding a roof rake. Hoist the rake onto the roof, into its middle. Pull the handle of the rake to scoop and drag the snow to the edge of the trailer's roof. Allow the snow to cascade to the ground. Clear as much of the snow as you can from this position.
Climb down the ladder when you can't safely reach any snow. Move the ladder to a new position, reascend the ladder and continue removing the snow. Repeat this process until you get to the end of that side of the trailer. Move the ladder to the other side of the trailer and continue raking the snow off the rooftop until all snow has been cleared.