Roch Mill is a low rubblestone building, approximately 6 x 5 metres and probably dating from the late eighteenth/early nineteenth century, attached to the mill house. A mill existed on this site by 1297, when it belonged to the estate of Roch Castle. The mill was still working in the early 1950s, producing animal feed.
Most of the mill machinery appears to have been replaced in 1868, from a date on the very short wooden upright shaft. The 12ft (3.6 metres) diameter overshot waterwheel had six wrought iron spokes and was mounted on a 4-inch (0.1m) square iron axle; it was replaced in 2007 by a new wheel replicating the original design, on a new axle and bearings. The axle originally turned in three bronze bearings, now four, and carries a 6ft (1.83m) cast iron pit wheel which drives a cast iron wallower and great spur wheel, the latter engaging with two stone nuts through wooden teeth. The wooden hurst frame, which contains some reused ship's timbers, was reached by a short wooden ladder. It supports two pairs of 4ft (1.2m) monolithic millstones made of a coarse quartz conglomerate, probably from Anglesey. The upright shaft reached only to the top of the hurst frame, and the upper bearing is missing. All ancillary machines and the drives to them have disappeared.
W J Crompton & B.A.Malaws, RCAHMW, from information supplied by D Smith, Welsh Mills Society, 9 September 2010 & site visit 18 October 2014.