I searched the Irish Family History Foundation's database.
A B rcd exists for Margaret Bruen, B 1854 (exact) in Ardcarne/Cootehill parish.
For Thomas Bruen B 1851, ditto.
For John Bruen, there are 2 B rcds for your era: 1846 and 1855, ditto.
For a John Bruen & Anne Farrell marriage, there are no matched pairs of marriage rcds in the same yr.
For Mary Hegarty, B 1858, Ardcarne parish, there is 1 B rcd.
For Patrick & Anne, there ARE matched pairs of M rcds in 1856, Ardcarne/Coothill parish, in Co. Roscommon. These are likely your ancestors. A view of the detailed rcd SHOULD show you their parents' names.
Google the Foundation's name to lead you to the database.