I use a Sunshield tarp that covers the roof and parts of the sides, front and back (depending on what size tarp is used). My Wife and I fold up the cover, accordian style, and I fold in the sides to make a manageable bundle. I tie a rope around the bundle, climb up the ladder, and hoist the bundle up with the rope. Then it is a matter of carrying the bundle to the front of the roof, unfold the bundle and drag it back across the top. Then it is back down the ladder and tie the cover down with rope and boat fenders half filled with sand. Bottles of pink stuff could be used also.
Note it is not an all-encompassing cover like CW sells which are too big and bulky for my taste.