When Roman law was rediscovered by eleventh century (and later) scholars, the version recorded by the rulers of the Eastern Roman Empire, Justinian in particular, became central to their basic understanding of its principles and application.
426 Law of Citations (Lex Citandi)
438 Codex Theodosianus
post-Theodosian Novels (Novellae posttheodosianae).
529 Codex Justinianus
533 Digesta or Pandectae
534 Codex Repetitae Praelectionis (2nd edition of CJ)
(after 534) Novellæ constitutiones
The leaders of Germanic tribes - the Ostrogoths, Visigoths, Franks, and Burgundians - taking over the area of the western Roman empire appreciated the advantages of having a written law, and ordered paraphrases and modifications of Roman law to be written down for their territories.
Terms such as (Roman) Vulgar law and "barbarized Roman law" have been used to designate the resulting documents - but modern practice prefers names reflecting the tribal/geographic/royal origins/attributions eg Salic Law, Breviary of Alaric etc. When embarking on literature searches it would be wise to use the older terms as well - such as Roman vulgar law - to ensure you do not miss some classic commentary.
Suggested subject searches in SOLO:
Roman law sources
Roman law history
Roman law interpretation and construction history
Roman law reception [followed by modern geographic area eg Spain]
as well as the specific names
eg Codex Hermogenianus