I've run accross some of these backs used. Can they be used with conventional 120/220 rolls and is there any drawback?

No, they will not take 120/220 film. It might be possible with some fairly major re-engineering, but not otherwise. They are designed only for 70mm perforated or unperforated film, in casettes similat to 35mm ones. Unlike 35mm, the film is not re-wound, but just passes from one cassette to another. They are much larger than a normal roll film back.