Rolls are measured by their width (x) by height (y) so if you measure 80, across and 60mm down your roll size is simply 80×60
Rolls come in 3 basic types.
To see if your paper is thermal, drag you finger nail across the front of the paper, if it leaves a distinctive black line then it is thermal.
Rolls bought from some retailers can appear to be “full” but they are not tightly wound and can in fact have less than 50% of a normal roll.
Also some rolls are made of a cheaper paper, this can leave dust and debris in the printer. This will shorten the life of your equipment and can cause lock ups, crashes and total failure.