Hello MIK, i also had a quick look at the civil record which commenced in 1864, from the births you give it appears the marriage may have been circa 1863 or 1864. I had a look at the RC parish records here for the various parishs, marriage would normally take place in the brides parish so assume Bailieboro or nearby, not sure the exact name of the religious parish of Bailieboro but looking at the map on the Registers website it looks to me that marriage records for the RC parishes are missing for these times you can look here https://registers.nli.ie/ I have noticed that while this is supposed to be all the RC records but on occassion I notice the subscription site Roots Ireland has records not here, I currently do not have access to it myself.
There are two private Facebook pages on Cavan Genealogy you could see if there is any information there or anyone who might know but if the record is not there it is not about unless you could identify siblings but not knowing at least one parent's name it is at best an educated guess.
I looked at Griffiths Valuation done in 1856 in Cavan or possibly late 1855 in Bailieboro and see 7 Rogers family and 14 Farrelly, did not check them all but see a Rogers and a Farrelly family lived in Tandragee, Henry Street, Bailieboro, possible they were neighbours but I was actually trying to locate the birth address of the children or where exactly they lived, if he was a labourer as stated on one certificate of birth you can maybe see if she was at her mothers place possibly for the 1st child, if the family even rented land he would probably describe himself as a farmer. It is supposition but all I can think of, http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
The Irish Genealogy site only has Civil records from 1864 (start year) for Catholics and Protestant marriages from 1845, all records from 1864, also most church records are not on the site and the registrs site does not have a search facility except year and month.
Good Luck
Pat
