Roan was chaplain to James Margetson, Archbishop of Armagh, who appointed him Bishop of Killaloe.[6] He was consecrated in June 1675 and was one of the few Anglican bishops to remain in Ireland during the subsequent religious strife of the Williamite war in Ireland, for which he suffered financially.
Roan died in office in 1692 at the Episcopal House at Killaloe and was buried in Killaloe Cathedral. His tomb is inscribed: "Hic jacet corpus Joannis Roan, S.S. Theologiae Doctoris, Laonensis Episcopi, qui obiit 5° die Septembris, A.D. 1692." (Here lies the body of John Roan, DD and Bishop of Killaloe, who died on 5 September 1692)[7]
^Clogher clergy and parishes : being an account of the clergy of the Church of Ireland in the Diocese of Clogher, from the earliest period, with historical notices of the several parishes, churches, etc" Leslie, J.B. p 33: Enniskille; R. H. Ritchie; 1929
^"Clogher clergy and parishes : being an account of the clergy of the Church of Ireland in the Diocese of Clogher, from the earliest period, with historical notices of the several parishes, churches, etc" Leslie, J.B p33: Fermanagh, R.H. Ritchie 1929
^Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1986). Handbook of British Chronology (Third Edition, reprinted 2003 ed.). Cambridge: Cambridge University Press. pp. 360–361, 396–398 and 434–435. ISBN0-521-56350-X.
^Ware, Sir James (1739). The whole works of Sir James Ware concerning Ireland, Volume 1. p. 598.