A mobile storage device comprises an exterior frame and an interior storage area within the exterior frame. The exterior frame comprises a seat for sitting on when the mobile storage device is not being rolled or moved. In some embodiments, the seat is movable from a closed position to an open position to access the interior storage frame. A flexible storage bag comprising one or more pockets is able be configured to fit within the interior storage area. In some embodiments, the exterior frame is adjustable to adjust a size of the interior storage area. In some embodiments, the exterior frame is collapsible for storing the mobile storage device.