Tradition was to marry in the bride’s church which in this case was Magheradrool Church of Ireland. So that would normally be the place to look for Rose’s baptism, siblings etc. (It might be Hugh’s church too, depending on what denomination he was). Unfortunately Magheradrool Church of Ireland’s early records were destroyed in the 1922 fire and so they have nothing before the 1880s now.
If Hugh happened to be Presbyterian, then Ballynahinch 2nd & 3rd churches have records from 1829 and 1820 respectively. Copies in PRONI in Belfast. I don’t think they are on-line anywhere.