I searched the Irish Family History Foundation's database. It contains 11,500,000 surviving rcds for abt 60% of Irish counties. Co. Roscommon rcds are in it. All Irish rcds B4 1840 are sparse.
For Catherine Murray (+variants) B 1828 +/- 4 yrs in Co. Roscommon, I found 17 B rcds. Using an "all Ireland" search instead of a county, I found 114 rcds.
Suggest you try to find some more info abt her from obits, headstones, etc. This will narrow the number of matches to a reasonable number. An exact date of birth, say 1828, would reduce the number to 1.