Czech vital records were kept in the predominant language for the area, apart from older records in Latin. That was Czech for most of the interior of the country and German for the border areas. With roughly 1/3 of the population German speaking German was one of the official languages of the kingdom of Bohemia. The female "-in" name ending is German, not Latin, and was the official female form of family names until about the beginning of the 18th century and in some areas preserved much longer. This is maintained in modern German for professions (Lehrer - male, and Lehrerin - female), places of origin (Berliner - male, Berlinerin -female) etc.
For Slavic incl. Czech names don't forget that they are declined, your Růzěny Sachsovy is really Růzěná Sachsová in the genitive case and not a valid name form. The same applies to males, whenever you see a male with the -ový name ending it's a declined form and the actual name is the form without this ending.