Is it accurate to state that Roman law was more significant in world development than its artistic and literary achievements?
This is, of course, a matter of opinion that cannot be objectively answered. I would argue that this is an accurate statement because of the impact that Roman law had on the development of European and American systems of law.
Roman law has influenced European and American systems of law in major ways. Roman law was written and placed in public displays. This made the law a tool that could be used even by common people. It also meant that there was a "rule of law" in which the laws were clearly set out and had to be obeyed by all people. This is in contrast to a system where the law is whatever the king says it is.
Roman law was derived much less from religious values than from others sources. This, too, makes it important. This is because it is seen as a major step (though only a step) towards the idea that the values of one religion should not be taken to rule a whole society.
Law has a huge impact on our everyday lives, much more than the impact of art or literature. Because law impacts us so much, and because Roman law has influenced our law to a huge degree, I would agree with the statement you have proposed.