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 parish, 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 Michael O'Malley B ???? somewhere in Ireland with the father's forename unknown, I found 715 B rcds. Suggest you search the censuses from 1910 back to 1850 to find info on Roger's parents. The censuses will at least let you est their DOB to within +/- 1 yr. Sometimes the specific cnty was entered. Also, naturalization papers often have more specific info than census rcds.
My g-grandfather came to Leadville in 1877. He lived on sixth street. He worked in the mines eventually becoming a general manager. He died ca. 1828 of miner's consumption.
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.