Hey Naomi Norbez! When the game tells you to roll back, it's only meant for demonstration purposes. In a "Hey, did you know you can go a few sentences back to re-read that bit in case you didn't understand?" kind of way. I assumed some people with no experience of Ren'Py mechanics would play the game, so that was my in-character way to teach them.
So in summary, rolling back won't get you new dialogue. Sorry for the misunderstanding!