Most of the useful records relating to family-history are now available online, many now free of charge... e.g. civil BMD records, Catholic Parish records, Griffith's valuation, Tithe applotment record etc, but as you've probably seen these often run out by the 1830s or so, especially for small farmer Catholic families. In this case both surnames are very common, which makes the search difficult...
I'm not sure if you have already looked into the Revaluation records, aka Cancelled Land Book, at the Valuation Office in Dublin city. These are not currently available online, but cover slightly later timeframe - i.e. they continue on from Griffith's Primary Valuation using the same type of format and continue up to the 1970s - see Valuation Office Dublin - Genealogy. The books for some counties have been scanned and are available to view on computers in the office, for other counties like Co. Wexford you have to request the various volumes. There's usually a new revision book every 15-20 years, the books are based on DEDs (Electoral divisions) and for rural areas the entries in th books are organised by civil parish and townland.
Bernard was baptised in the Catholic Parish of Newtownbarry/Bunclody, which at the time covered parts of five civil parishes - Ballycarney, Kirush, Monart, St. Mary's Newtownbarry and Templeshanbo. Rossard townland is in Templeshanbo civil parish. Unfortunately there are the gaps you've seen in the baptism records for the parish during the 1850s, and the registers start about 1834. Marriage records are recorded back to 1834 - I checked for possible marriage for your Thomas and Winifred in this parish but didn't find any matches, extending the search to other parishes in the area also did not show any promising results. Likely they married in a parish that does not have records going back far enough, or their marriage was noted on a page now missing or too faded to read..
There are some details for the civil parish of Templeshanbo included in Lewis' Topographical Dictionary of Ireland 1837 which might be of interest - see Templeshanbo, Co. Wexford, and also details for the town & civil parish of Newtown-Barry/St. Mary's.