The geographical centre of Ireland is located on the western shore of Lough Ree in the south of the county.

[6] Roscommon is the third largest of Connacht's five counties by size and the second-smallest in terms of population.

In 2008, a news report said that statistically, people from Roscommon have the longest life expectancy of any county on the island of Ireland.

North Roscommon South Roscommon Rathcroghan (Irish: Rath Cruachán), near Tulsk, a complex of archaeological sites, the home of Queen Medb (Irish: Méadhbh, anglicised Maeve), was the seat of Kings of Connacht and then to the High Kings of Ireland.

This was the starting point of the Táin Bó Cúailnge, or Cattle Raid of Cooley, an epic tale in Irish mythology.

In 1585 during the Tudor re-establishment of counties under the Composition of Connacht, Roscommon was established with the South-west boundary now alongside the River Suck.

A "well defined" and "original" fine metal workshop was active in County Roscommon in the 12th century.

[13] John O'Donovan (1806–1861), historian and scholar, visited County Roscommon in 1837, while compiling information for the Ordnance Survey.

Here I am stuck in the mud in the middle of Loughs, Turlaghs, Lahaghs and Curraghs, the names of many of which are only known to a few old men in their immediate neighbourhood and I cannot give many of them utterance from the manner in which they are spelled.

Roscommon have captured the Connacht Senior Football Championship on 23 occasions, the most recent being in 2019.