Thank you for your message.
Just to clarify, did the database where you found the information about Matthew and Frances' wedding mention the parish of Ross specifically? If it did, then you are on track to find information on the family. However, if it did not you need to try and find out which parish in the diocese of Cork and Ross they originated from. This will help narrow down your search for their church records.
Regarding Church records. Baptism certs can be used to find out parent's names, which in turn will allow you to look up any baptism records of siblings. Marriage records can sometimes give information on occupations and residences in addition to names etc.
Most Catholic records are held locally. One website which may be of help is the irishtimes website where they give an overview of what records are available in specific parishes. For the parish of Ross/Roscarberry follow this link:
Also, both Catholic and Church of Ireland records from the pre 1900 period are currently being uploaded to www.irishgenealogy.ie/index.html free of charge. However, as this is an on-going project not all records are available yet.
You could also do a check for any Talbot's and Justice's that remained in Ireland in the Tithe Applotment Books. These are land records compiled between 1823 and 1837 in order to determine the amount which occupiers of agricultural holdings should pay in tithes to the Church of Ireland. If you could find John, or any other members of the family in these it would confirm the parish they lived in. You can search this here:
Some other websites which may help you are:
The National Archives of Ireland http://www.nationalarchives.ie/genealogy1/genealogy-records/introduction/
The National Library of Ireland http://www.nli.ie/en/family-history-introduction.aspx
The National Archives UK ? genealogy search: http://www.nationalarchives.gov.uk/records/looking-for-person/
The Public Records Office of Northern Ireland http://www.proni.gov.uk/index/family_history.htm
US National Archives/Immigration info: http://www.archives.gov/research/immigration/
Family Search: https://familysearch.org/
I hope that this helps. Remember to post as much information as you can with regard to the people you are researching. The more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.