No Roman Emperors ever created or attempted to put in place a law to free Slaves in the Empire. Over time Slaves went from simply being property to gaining rights, like being able to "own" a piece of land (which was typically owned by the Master), and even being paid (which led to many Slaves actually being able to purchase their own freedom). Slaves were never freed en masse but it wasn't rare to see them freed for doing good deeds, or out of respect from their Masters. In the event of a Masters death, Slaves could be freed through testamentary manumission which was only an option if the Master gave permission for the Slave to be freed in their will. A large amount of Slaves weren't freed though, with the only ones that were typically being educated, however manumission (not just testamentary, but simply the act of freeing ones Slaves) became so common that Augustus actually ruled that a Slave must be at least 30 to be freed. Mostly because freed Slaves actually became full citizens and gained the same rights and privileges as any other normal Roman (things like voting and holding office). So no, not a single Roman Emperor ever sought to end slavery, and no major Roman figures during the time of the Roman Empire ever sought to emancipate the slaves either.

When did slavery end in West Europe?