To quickly explain: many Biblical names where not 'translated' into Irish-Gaelic when Christianity spread to Ireland. Instead a good many were 'equated' to existing Irish names. This will explain why many English names have multiple Irish forms and often appear incongruous.
That said, Sorcha is likely the most common form of Sarah in use. Other names that are sometimes equated to Sarah are Sadhbh, Saraid, Mórach and Mórag.
Judith has never been extremely common in Ireland, but when rendered in Irish it is usually made Síle or Siobhán.
Now the Irish Bible was written later, and almost all names within have since received proper 'transliterations' into the spelling rules of Gaelic. These Gaelicized forms are interesting and rather attractive, but have never really been taken up for general popular use. In the Bible, Sarah is Sárá and Judith is Iúidit.
I must disagree with Keesa's post, Róis has an accent over the 'o' and should be pronounced [ROESH].
The many names I've listed here should have links to their individual entries, but I will list out pronunciations of these names as I understand them: