The pre-Norman Cantref of Rhos was a Medieval administrative division, which became the Hundred of Roose and was formalised by the Laws in Wales Acts 1535–1542.
However archaeological discoveries in Pembrokeshire as early as the 1920s by Sir Mortimer Wheeler at Wolfscastle earlier Iron Age and Roman coinage and artefact discoveries, and recent excavations by the Dyfed Archaeological Trust under the direction of Heather James at Carmarthen (Maridunum) in the 1980s point convincingly to Roman penetration to the westernmost parts of Wales.
The strategic position of Haverfordwest with its defensive bluff overlooking the lowest fordable point on the Western Cleddau accessible to sea traffic suggest a Roman origin probably modest in scale for the town from about 96 AD.
The ecclesiastical centre (perhaps the seat of a bishop in the Age of the Saints) was probably one of the several churches of the local St. Ismael, most probably St.
[2][3] The hundred, with its capital at Haverfordwest was the original centre of the Norman/English "plantation" in the 12th century, and it has been essentially English-speaking since then, forming the core of Little England beyond Wales.