When practicing new movements, it's always good to have a back up plan or exit strategies just in case you attempt fails. As a simple example, if you are learning how to jump, one of your first lessons should be learning how to land. Same goes for learning and executing a Muscle Up. Whether successful at the attempt or not, the athlete should know how to safely come down off the rings other than just letting go or falling through. Without knowing how to roll out of the rings, athletes are at huge risk of shoulder injuries because of missed reps.
In this video, Coach Carl demonstrates how to perform a Roll Out on the rings. First, Carl scales with the movement with some assistance from a band to control the rings so they don't separate when performing the Forward Roll. The band also acts as a support across the front of the hips to ensure the athlete feels how high the hips should be - coming over the top of the hands and rings. For more support, keep the band tighter. Then as the athlete progresses, add more slack to the band until the band is no longer needed.