Rosanna and Ann are,indeed, elusive. There are no obvious marriages for them nor burials but they don't appear in the censuses with their maiden names(using any of the Bailey variations). Mum and Dad are still in Wilsford in 1851. One brother and his family are also there and another in Upavon,but this you know. I've checked as many burials in the area pre-1837 as I can,including all the Manningfords, Wilsford,Upavon and Pewsey. Their father was from the latter,I believe , and mum was from Abbots although baptised in Bruce? I've tried the London listings too in case they went into service there but no joy.
Sorry not to have been of any use so far but nil desperandum!