Does water roll off when this is used on an outdoor patio, or does it absorb or retain the water in the rug?

Our 1/4" Tough Rubber Rolls are somewhat porous and will allow water to run off of the roll if it's on a grade. If there is no grade, then the water may collect on top of the roll. The water would evaporate, but any salts or sediments will make their way into the pores in the floor.