If you are a student and have access to a scholary database then you should have easy access to Justinian's Corpus Juris Civilis which is the main primary source for Byzantine laws and codes and remained the foundation for legal framework in Europe for centuries.

If you do not have access to a database you can get it on Amazon for roughly $16. That's the price I found on a quick price check.

To have a better understanding of the codes it may be helpful to look up previous Imperial laws as well. There are many readily available works from Diocletian. The time periods between Diocletian and Justinian encompasses the fall of the western empire and therefore should provide a clear delineation between "Roman Laws" and "Byzantine Laws".

It is important to also understand that the Juris Civilis was collection of all laws and codes that Justinian's magistrates considered to be important or relevant so the document includes many laws that would have been considered historical at the time of the documents creation.

Please let me know if this has been helpful.