How have you set up your read only root?
I recently set up a bunch of Pi with read only root using an overlay file system such that any and every program can still write any files it wants to. But the overlay fs causes all those writes to go to copies of file in RAM. On reboot the RAM overlay is reinstated with the underlying, read-only, files.
I used the instructions here: viewtopic.php?f=63&t=161416
This is a really elegant and simple solution to the read only root problem.