The Devenish family were resident in county Roscommon from the 17th century. By the late 18th century William Devenish was living at Rush Hill. The families of two of his sons were resident at Rush Hill and Mount Pleasant throughout the 19th century. At the time of Griffith's Valuation one of his younger sons, Robert Devenish, held land from Reverend William Handcock and also from William Lloyd in the parish of Aughrim, barony and county of Roscommon and in the parish of Kilmore, barony of Ballintober North. Robert's older brother, John Devenish, held land in the parish of Lissonuffy, barony of Roscommon. Over 600 acres of the estate of John Devenish was offered for sale in the Landed Estates' Court in July 1873. These lands were situated in the baronies of Frenchpark and Roscommon. The Irish Times reported that they were sold to John Grady and Thomas Conry, the sales realising over £7500. In the 1870s George Devenish, of Delgany, county Wicklow and John Devenish of Rushill, Drumsna held 54 and 35 acres respectively in the county while John Devenish of Mountpleasant, Strokestown, still owned 597 acres.
Gilbert Mahon held land in the parish of Lissonuffy, barony and county of Roscommon in the mid 19th century. The ''Landowners of Ireland'' record Gilbert Mahon "now John Devenish", Rushill, owning 365 acres in county Roscommon in the 1870s.