Skalds are employed at various administrative tasks. Their job is to preserve the knowledge of the Known World.
The exact job description of a Skald likely varies depending on whether they are civillians or military. Skalds compile maps, copy Pre-Rash books, and keep records of the human activities since the outbreak.
Skalds also keep knowledge of languages other than the ones spoken in the post-Rash society available, but both skalds with such expertise and documents written in those dead languages are very scarce.
Like mages, it seems to be common for skalds to perform other jobs in addition to administrative duties, especially in smaller settlements.