Rossnowlagh, "the apple wood", is a parish and village on the south coast of Donegal, to the west of the Donegal to Ballyshannon road. The parish was created originally as a perpetual curacy out of its neighbour, Drumholm, in 1831. The church was consecrated on 21st September that year, and dedicated to St. John. The Church is entered through a small porch at the west end, over which is a bellcote. There are two windows, each of two lights in the side walls, as well as a window with two lights above the porch. There are three windows of two lights in each side wall of the nave. The east window, which has three lights, is of stained glass and depicts the Risen Lord at the empty tomb. It commemorates Francis Jennings, his wife and three of his daughters, and is dated 1951.
The sanctuary is separated from the nave by three-sided communion rails, set into which, on the right side, is a prayer desk. The vestry room is to the right of the sanctuary. The Holy Table is in memory of Robert Hannah, and is dated 1932. Outside, and to the left , is the pulpit, before which stands the font. The lectern on the right side of the nave commemorates Robert Gray. There is a one manual organ by Evans and Barr of Belfast in the south-east side of the nave.
A plaque records the dedication of the lighting and heating systems in 1955 in memory of William and Hannah Smyth. Another plaque records the dedication of the entrance gates in 1963 in memory of the Thompson family. Another plaque on the west wall records the re-hallowing of the church after extensive renovations in 1995.