I searched the IFHF database at ROOTSIRELAND.IE. It has abt 19M B/M/D records for MOST Irish counties.
For John Minton B 1841 +/- 5 yrs, somewhere in Ireland, with a father forenamed John, and a mother forenamed Bridget, I found 1 record. The exact B year is 1841. The County is Kilkenny.
This record may or may not be for this ancestor. Kilkenny is some distance from Roscommon or Mayo. Suggest you visit the database and search for John's siblings. If you find B rcds for them in Kilkenny for the correct Year, this may lend credence to my findings above.