Eagan/Egan family in Oran Parish, County Roscommon

I'd like to ask for assistance researching my Eagan/Egan ancestors in this parish - I'm aware there are no surviving Catholic Church records, so will likely have to depend on finding a gravestone and using land records, along with some y-DNA testing. My ancestor John Thomas Eagan b. May-1844 and his brother William b. abt. 1841 in Oran Parish were sons of Thomas Egan and Mary Keefe. According to William's 1915 obituary, his father Thomas died in about 1850, after which the remaining family moved to Manchester, England to work in the factories there and earn money for ship passage. By the early 1870's they had made their way to the US, with John and William settling in southern Colorado.

I believe the father Thomas may be buried in the Oran Cemetery in Carroweighter townland. I see at Find-a-Grave (https://www.findagrave.com/cemetery/2489977/oran-cemetery) that there are a relatively small number (207) memorials recorded of what looks to be a really good-sized cemetery. I see only one Egan there - Mary Jane Egan Freehily d. 1924. The earliest date of death appearing in that subset of records is 1864, so I'm wondering a) how early the cemetery was in use, b) what are the chances there is an 1850-era headstone that has survived and is readable, and c) Are there early headstones for Egan family members, including Thomas?

I'd greatly appreciate assistance with the cemetery headstones and any direction on 1850 and earlier surviving land records for Oran Parish. I hope to visit Ireland in the near future to do boots on the ground research.

Regards,

Tony Popish

Centennial, Colorado, USA