The Senate and the Emperor decided -- at times. The Roman Empire spanned a long, long time and in various times the laws were created differently. Ideally, the senate was to propose a law and then the voting assemblies voted to either pass or reject it. However this was not always practical, so the senate got around this by passing "resolutions" that had the effect of a law. When the principate came into power, it was the emperor who proposed the laws and the senate, if it knew what was good for it, ratified the emperor's proposals into law.
Both empires shared similar laws and traditions.
Both the Roman and British empires influenced the regions of their worlds that they conquered or occupied. Both empires introduced their laws and cultural values the empires had. Both empires also recruited members of these regions to become part of their military forces.
They were Hastushas and there were 10 of them.
Empires are not people. Therefore, they do not eat.
Roman and Han empires
Empires do not standardise each other.
Burning Empires was created in 2000-04.
The answer is the Roman Empire
They created large empires containing many national groups.
Empires of Eden was created in 2008.
Young Empires was created in 2009.
Fantasy Empires was created in 1993.