For sizing the motor it sounds like the key thing will be speed and acceleration. How fast do you need to get the roller to full speed? If you do use a servo your max speed might be 3500 RPM as an example, so if you only need a 1000RPM roller (note you get a natural reduction due to the roller being a smaller dia than the film) you can put a 3:1 gearbox no dramas.
If you can tolerate a 3-5 second acceleration time then the required torque will be tiny. Maybe less than 1nm or so. Something like a AB TLP 70mm circle might do the trick.
There are calculators you can use for single mass rotating on its axis, then what ever torque you come up with you can reduce by the ratios of the rollers, and then the gear box. This could help:
https://www.engineersedge.com/motors/calculator/accelerating_torque_force_solid.htm