Utterly great game, and now as a full grown man I can play it through and not just cower in terror from skeletons as I did when it first came out.

BUT! One small thing is the (deep, engaging) characters in FMV have a slight lag against their actions, so their mouths move then half a second later, possibly a bit more, their voices are heard. Most degrading for some who are risking so much for the fate of the world.

Any things I can meddle with in dosbox? Bit disheartened now I've checked the forums and no other mentions of it.

First make sure this really is an emulation problem. In general the audio in these movie files is never quite in sync with the video, there is nothing that can be done about that (It looks to me like they recorded some of the dialogue audio separately from the video). There are only a few sequences where video and audio are really noticeably out of sync, though.

If you find it is a consistent lag, edit the "dosboxROTH.conf" file in the game directory and look for the settings "blocksize" and "prebuffer" and lower these values (use powers of 2 for the blocksize, like 256, 512, 1024, 2048, etc.). This will decrease audio lag, but will increase the probability of audio stuttering, so you will need to find a balance that works for you.

In general: The better you processor, the lower you can risk making these numbers without getting too many stutters.