Many people have told me that they use 120 film successfully in their 620 cameras. I use to always reroll 120 onto 620 spools to use these cameras but with so many people responding I've done abit of testing and have found that MOST of my 620 cameras will accept 120 film without rerolling while some do not. To find out if your camera does may destroy a roll of film but could save you alot of money in the long run.
Load the 120 in as usual and use a 620 spool for the take-up. You will find that you've got to roll a good amount onto the take-up spool before closing the camera, not so much as to expose film, but enough to come up to the "arrow" line printed on the film. Do this in very subdued light if you can. With the camera then closed, roll the film gently, especially if you feel it not rolling easily. If it advances then you've made it, if not you'll have to use prerolled 620 or roll it yourself.
For a good place to get your 120 film right now click on Cameraworld.com.
Roll Your Own #620 Film
If you are shooting with 620 film you can save yourself
some money by rolling this yourself fairly easily.
620 is basically 120 on a smaller diameter
spool. If you have 620 spools go into a light-tight
room and unroll the 120 film, paper and all, and as tightly as you
can re-roll it onto the 620 reel. When you get
to where the film ends (begins really) gently
untape the film from the paper and retape it to
the paper smoothly as you continue to roll. Load and unload the camera
in subdued light and you can shoot with that old
620 camera. The numbers even show thru the window correctly for every camera and format! It may take a couple of tries but
you'll get the hang of it!