A wide variety of records, many of which are relevant to Irish genealogy and local history and include the Convert rolls, Calendar of wills, as well as the Census and Tithe Applotment records are held at the National Archives 

The 1901 and 1911 Census returns contain wealth of information, including names, ages, literacy and property ownership.

The Tithe Applotment Books (1823-1837) contain records of tithes paid for almost every parish in Ireland, including in the record the name of the occupiers and the amount of land held.

Griffith's Valuation (1847-1864) is the first full-scale valuation of property in Ireland. It is one of the most important surviving nineteenth century genealogical sources.

Catholic Parish Registers contain records of baptism and marriages from the majority of Catholic parishes in Ireland. 

County Roscommon Heritage and Genealogy Centre is the designated local centre of the Irish Family History Foundation and offers a professional and bespoke research service to people with family roots in Roscommon.

Leitrim-Roscommon Genealogy site is a very useful resource for maps showing civil and Catholic parishes and townlands.