Which one? What sort of exception? In particular, is it dosbox itself or the game that's giving an exception? I don't use Ubuntu, so I have to ask: what version of dosbox? Did you remove the "overlay" mount (used for Galaxy cloud saves, not available on Linux, and you'd be better off using unionfs-fuse or something like that if you want overlays, since there are some issues with dosbox's overlay)

I use the default dosbox configuration myself, with slight customization, and only use the *single.conf file contents from gog. The only config options I copy from the main/shared config are the CPU cycle limits. I also enable mt32 for roa1-2 and correct the paths in game.inst in roa3. This has worked without issue for years.

I run the series via Lutris. No issues in RoA1 and RoA2 so far, but Riva is still misbehaving.