Roman law is a huge topic. In other words, there are too many important laws/principles to mention. In light of this, let me give you a sample of some of the most important principles.
First, the Twelve Tables, Rome's earliest laws were made public to give parity to all people. Before this time, only the elite of Rome knew the law. This situation obviously favored the aristocracy. The publishing of the Twelve Tables, therefore, was a watershed moment.
Second, the Licinian Sextian Acts of 367 put an end to the struggle of the orders. This law allowed all classes of people to run for office and hold Rome's highest office. This fact helped to create equality.
Another important principle of Roman law is that it took its shape from various sources. For example, according to Cicero, equity, custom, decided cases, legislation of assemblies, resolutions of the senate, edict of magistrates, and the decision of the jurists can be sources of law.
Finally, Roman law used social pressure to uphold the importance of law and order. In other words, it was the job of the pursuer to get the defendant to court and in a shame based society it is believed that the defender would come, even if he was more powerful to protect his reputation. If this did not work, the Praetor could treat the defendant as in hiding and sell as his property