There was no fixing this, we tried.
Easier and free, use a roll of background paper for this!
Hi Dominique. As Bob said, our reverse roller is basically the inner cardboard core of 44" roll paper. A 2" or 3" section of PVC will work as well. It's just easier to maneuver if the sheet that envelopes the print is glued or otherwise affixed to the core. Just make sure there is nothing sticking out that will leave an impression on the print.
Just roll the print with a piece of brown thin wrapping paper and tape this. I have mailed thousands of 20x30 prints this way.