Dear annieliz
Welcome to Ireland Reaching Out!
As a matter of interest have you tried searching Ancestry.com for any mention of your ancestor?s name in member family trees or messages?
I have had a look on www.rootsireland.ie and the only marriage for a James Fitzpatrick to a wife surname Kelleher is in Co. Cavan in 1885. If this is the correct marriage certificate you can apply online for the civil marriage ceritificate from the GRO in Co. Roscommon and learn the details of their parents? names (which you already have but can confirm) and most importantly their townland and parish:
http://www.hse.ie/eng/services/list/1/bdm/Certificates/
Let me know if you think this Cavan record is relevant, it might not be but at least you can rule it out.
Best wishes
Clare Doyle
Genealogy Support