For Joseph Fallon B 1880 +/- 1 yr, somewhere in Ireland, with a father forenamed Chri(stopher), I found 0 rcds. Expanding the search to all Ireland and all dates, I found 2, 1876, Co. Roscommon, Ballyleague CP, and Kilgefin/Cloontuskert RC parish. Are you sure of the DOB?
For Christopher Fallon M 1872 +/- 4 yrs, Co. Roscommon, I found 1 rcd: 1875, Ballyleague CP.
For Mary Barlow M ditto, ditto. These are likely for your ancestors. A view of the detailed rcds SHOULD reveal their parents' names.
For Christopher Fallon B 1850 +/- 5 yrs, Co. Roscommon, I found 0 rcds.