I occasionally use a "23" Graflex 6x9 roll-film back on my Tachihara 45GF.
The roll film holder is mounted on a home made adapter that replaces the ground glass back of the Tachihara. In use the image is focussed and framed on the regular ground glass which has been marked out with 6x9 format lines. Then the sliding clips that hold the ground glass back on are opened, the GG back is taken off, the RF back and adapter are put on, and the exposure made. The whole process is a little cumbersome in the field but in view camera work speed is usually not a priority. Making the adapter needed only basic woodworking skills although getting the film plane and ground-glass plane to coincide exactly needs some subtle shimming.
If I am after a faster sequence of exposures I use a Toyo 6x9 sliding back on the Tachi. This is adapted to the camera in a similar way to the "23" Graflex back but because it has its own ground glass screen it doesn't have to be taken on and off the camera between shots. I don't have a Toyo 6x9 roll film holder so I just use a Mamiya RB67 back and get 10 shots on a roll instead of 8. Because the sliding back has some stand-off from the rear of the Tachi short focal length lenses (90mm for example) can't be brought to infinity focus; 210mm works fine.