A retractable cover for a slide-out unit on a recreational vehicle, mobile home, travel trailer, or the like, includes a roll bar that is movable with the slide-out unit away from the side of the vehicle with the roll bar mounted in a housing having a closure plate which is easily pivoted to an open position or removed to facilitate maintenance or removal of debris that may accumulate in the housing during a retraction of the cover. The housing is mounted on the slide-out unit with brackets permitting the brackets to be located at any position along the length of the housing and also permitting the housing to assume a length that is much greater than the width of the slide-out unit providing a better cover for the slide-out unit during inclement weather.