Rock Woollen Mill was built in 1890 by John Morgan, great-grandfather of the present owner. It has two storeys, built on a steep bank above the Afon Clettwr with a basement storey supporting the east end. The walls are of rubblestone and the roof is slated. The windows have slate sills, those on the ground floor having cambered heads of stone voussoirs, and those above having wooden lintels. There are twentieth-century extensions including a lean-to on the north-west end of the mill, and another building to the south-west.

A 130 metre lon leat from Pont-y-Foel Weir (NPRN 420052) supplies a rare example of a double-width overshot water wheel, supplied by the Bridgend Foundry, Cardigan, which powers the carding and spinning operations inside the woollen factory, as well as producing electricity via an alternator. The mill contains a complete set of working machinery, some of it modern. All the woven articles and yarn produced in the mill are for sale in the mill shop.
(Sources: Association for Industrial Archaeology: A Guide to the Industrial Archaeology of Mid-Wales, 1984; Welsh Mills Society published leaflet, 1999; Owner, during a site visit by B.A.Malaws, RCAHMW, 26 October 2002)
W J Crompton, RCAHMW, 21 October 2014