In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Rhostie like this:
RHOSTIE, or Rhosdhu, a parish in Aberystwith district. Cardigan; near the coast, 6½ miles S E of Aberyst-with r. station. Post-town, Aberystwith. Acres, 1, 307. Real property, £482. Pop., 122. Houses, 27. The living is a rectory in the diocese of St. Davids. Value, £101. Patron, the Bishop of St. Davids.
A Vision of Britain through Time includes a large library of local statistics for administrative units. For the best overall sense of how the area containing Rhostie has changed, please see our redistricted information for the modern district of Ceredigion. More detailed statistical data are available under Units and statistics, which includes both administrative units covering Rhostie and units named after it.
GB Historical GIS / University of Portsmouth, History of Rhostie, in Ceredigion and Cardiganshire | Map and description, A Vision of Britain through Time.
Date accessed: 31st July 2016
Click here for more detailed advice on finding places within A Vision of Britain through Time, and maybe some references to other places called "Rhostie".