Please describe the layout that you want to print to this printer.
You may be handle this issue with at least one field on your object sized very tall and then set to slide up/resize enclosing part via settings in the inspector.
But I could be wrong here. Haven't tried printing from FileMaker to a continuous roll printer so this one's a new one on me...
I wound up setting the print size to the maximum size of the largest field and it just prints a new "page" for each entry.