I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For Ann Shanly B 1845 (exact) in Co. Roscommon with the father's forename Bernard, I found 0 rcds. There is one rcd for this name, but the father's forename begins with "M."
For Ann Shanly B 1824 +/- 4 yrs in Co. Roscommon with the father's forename unknown, I found 0 rcds. There are B rcds in other Irish counties: 1826 Mayo, 1826 Longford, 1826 Leitrim, and 1827 Dublin. You will need an exact DOB, parent(s) name(s), and/or placename to pick which, if any, is for your ancestor.
For Bernard Feeny B ditto, I found 3 rcds in Roscommon (1820, 1821, and 1828), and 1 in Galway (1823).
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.