Currently gamut mask selection and rotation are not saved. In order to be able to continue work on the same file consistently, both the selected mask and its rotation should be saved into the Krita file. Without this the only way to ensure consistency between work sessions is by writing the selection and rotation down and manually restoring it.
Hi, Storm Engineer, thanks for the report. There is a plan for similar feature, details are available in Phabricator: https://phabricator.kde.org/T9652. It is not fully designed yet, it needs ideas and UI mockups. If you are interested and have some time to spare, I will be happy to work with you.
The task says it's "Resolved" but it doesn't seem to be working. And frankly, I believe it should be upgraded to a bug - I mean you use a gamut mask per project anyway, and writing down the rotation sounds icky. (And the rotation and gamut mask is not even saved into kritarc). Gamut mask, as a resource, will be possible (to implement) to save into the document in the new resource system.