It depends somewhat on whether you're talking about the Republic or the Imperial times.
The behavior expected of married Roman women (Roman matrons) was that they would support their husbands, have lots of children (Augustus gave special privileges to mothers of 3 or more children), and keep themselves modestly busy in their households, spinning and weaving, teaching the children, and otherwise upholding the "Roman Virtues."
Prostitution was a recognized profession, although not one that respectable women aspired to.
Incest was a huge taboo. Caligula committed it regularly with his sisters, and even treated one of them as his wife (before he murdered her). And later, Claudius decided to marry his niece, but that would have been incestuous. So he changed the laws that forbade uncles and nieces to marry. However, cousin marriage was considered okay and normal.
Nero was married to Claudius' daughter, Octavia -- which would technically have been incestuous, since Claudius had adopted Nero as his son, so one of Claudius' friends adopted Octavia to provide the legal fiction that Nero was not actually marrying his sister (which he wasn't anyway -- Octavia was actually Nero's cousin... I think

).
It can really take a scorecard to keep track of all this -- there was a short while during Claudius' marriage to his cousin Messalina when Messalina and Agrippina (Nero's mother) were simultaneously each other's aunt and niece!
