[Marcus Tullius Cicero, 1st century, Musei Capitolini, Source: Wikimedia Commons]
As time went on, both the Roman legal system and public opinion became a bit more even more open to divorce. At least part of this probably had to do with the fact that the only legal basis for marriage affectio maritalis, essentially the intent to be married (which I've talked about before here).** As a result, if a couple (or one of their fathers if one or both of them were still legally under a father’s power) decided that for some reason they lacked that intent, they had every legal right to dissolve their marriage.
By the time of the Empire the law had very little to say about the conditions under which one could or should divorce other than Augustus’s decree that a man must divorce his wife if she were convicted of adultery. For the most part, jurists focused their energies on dealing with the consequences of divorce. When a woman divorced, her dowry was returned to her, minus one-fifth of it per child she produced, and she or her father had the legal right to sue if she did not get it. Her husband retained an additional sixth of it if she had committed adultery. If woman found she was pregnant within thirty days after a divorce, her ex-husband was legally required to recognize and support the child.
This isn’t to say that Romans moved in and out of marriage as they willed. Marriage was still the socially preferred state for Roman citizens, but forcing people to remain married in perpetuity was never considered an option.
*It’s worth noting that though a wife was not permitted to divorce her husband, there was a way in this time period for her to retain the respectability of the married status while avoiding being legally under her husband’s control. By absenting herself from his household for three nights in a row every year, she interrupted his prescriptive right to her. (Table VI) This practice fell out of favour by the time of the Empire. (Gaius, Institutes 1.111)
**Not necessarily love. Yes, the literal translation of the term is “marital affection,” but it’s important to remember that romantic love wasn’t really considered a factor in western European marriages until the Modern period. In a lot of marriages this had to do with politics on one scale or another.