[1] The Roman era would see Cantref Coch pacified, and even become a center of religious and industrial activity, as well as the location of an important road (the Via Julia Maritima) from Glevum into South Wales.

[2] During this period, the production of iron ore and charcoal increased rapidly, which would have strengthened the areas links with the administrative centre for these industries at Ariconium.

[3] The community at Ariconium existed prior to the Roman invasion and was home to a number of ancient bloomeries, suggesting preexisting trade links with Cantref Coch.

[6] It is generally thought that Ariconium was a latinisation of an existing British Celtic name, and that the post-Roman polity of Ergyng represents a continuation of Pre-Roman or Romano-British culture.

[10] Iolo Morganwg called Cantref Coch the third part of the kingdom of Iestyn ap Gwrgant, separating it from both Gwent and Morgannwg proper (Glywysing).

However, the areas commonly referred to as Rhwng Gwy a Hafren was located further north in Powys, rather than in the locality of the Cantref Coch.