This is from Wikipedia as I can't find the relevant book on my shelves (did my Masters dissertation on ancient Roman women and also have had several glasses of wine
During the classical era of Roman law, marriage required no ceremony, but only a mutual will and agreement to live together in harmony. Marriage ceremonies, contracts, and other formalities were meant only to prove that a couple had, in fact, married. Under early or archaic Roman law, marriages were of three kinds: confarreatio, symbolized by the sharing of bread (panis farreus); coemptio, "by purchase"; and usus, by mutual cohabitation. Patricians always married by confarreatio, while plebeians married by the latter two kinds. In marriage by usus, if a woman was absent for three consecutive nights at least once a year, she would avoid her husband establishing legal control over her. This differed from the Athenian custom of arranged marriage and sequestered wives who were not supposed to walk in the street unescorted.
Divorce
Divorce was a legal but relatively informal affair which mainly involved a wife leaving her husband?s house and taking back her dowry. According to the historian Valerius Maximus, divorces were taking place by 604 BC or earlier, and the law code as embodied in the mid-5th century BC by the Twelve Tables provides for divorce. Divorce was socially acceptable if carried out within social norms (mos maiorum). By the time of Cicero and Julius Caesar, divorce was relatively common and "shame-free," the subject of gossip rather than a social disgrace.[54] Valerius says that Lucius Annius was disapproved of because he divorced his wife without consulting his friends; that is, he undertook the action for his own purposes and without considering its effects on his social network (amicitia and clientela). The censors of 307 BC thus expelled him from the Senate for moral turpitude.
Elsewhere, however, it is claimed that the first divorce took place only in 230 BC, at which time Dionysius of Halicarnassus notes[55] that "Spurius Carvilius, a man of distinction, was the first to divorce his wife" on grounds of infertility. This was most likely the Spurius Carvilius Maximus Ruga who was consul in 234 and 228 BC. The evidence is confused.[56]
During the classical period of Roman law (late Republic and Principate), a man or woman[57] could end a marriage simply because he or she wanted to, and for no other reason. Unless the wife could prove the husband was worthless, he kept the children. Because property had been kept separate during the marriage, divorce from a "free" marriage was a very easy procedure.[58]
An emancipated woman legally became sui iuris, or her own person, and could own property and dispose of it as she saw fit. If a pater familias died intestate, the law required the equal division of his estate amongst his children, regardless of their age and sex. A will that did otherwise, or emancipated any family member without due process of law, could be challenged.[40] From the late Republic onward, a woman who inherited a share equal with her brothers would have been independent of agnatic control.[41]
As in the case of minors, an emancipated woman had a legal guardian (tutor) appointed to her. She retained her powers of administration, however, and the guardian's main if not sole purpose was to give formal consent to actions.[42] The guardian had no say in her private life, and a woman sui iuris could marry as she pleased.[43] A woman also had certain avenues of recourse if she wished to replace an obstructive tutor.[44] Under Augustus, a woman who had gained the ius liberorum, the legal right to certain privileges after bearing three children, was also released from guardianship.[45] The role of guardianship as a legal institution gradually diminished, and by the 2nd century AD the jurist Gaius said he saw no reason for it.[46] The Christianization of the Empire, beginning with the conversion of the Emperor Constantine in the early 4th century, eventually had consequences for the legal status of women.