The Crith you are looking for is in the civil parish of Kilmeane, Co. Roscommon. The clue is in your reference to St. John’s. The parishes of St. John’s and Kilmeane now form part of the modernCatholic parish of Knockcroghery, which is on the main Athlone to Sligo road, roughly halfway between the towns of Athlone and Roscommon. The official spelling of the townland name is Cruit (same sound but different spelling). Good luck with your research!