A possible scenario:
In 1871, I can only find one 17yr old Mary Ann Roach, working as a servant for the Young family on Greys Inn Road. Mary Ann born Ratcliffe Highway.
In 1861, there is a 6 year old Mary Ann Elizabeth Roach, born Middlesex, living with Samuel Roach, wife Sarah, son Henry, D in Law Ann Smith and another family unit George Smith, wife Catherine and infant George Alfred, at 8 Cromer Street, RG9 105. Strangely, no relationship is written for Mary Ann Elizabeth and she was the only one Middlesex born - Samuel, Sarah, Henry Roach and Ann Smith were all born in Gloucestershire. Samuel Roach married Sarah Smith in 1858, so Mary Ann E could be their illeg daughter or the illeg daughter of one of Sarah's son's or daughters .
I wondered if Mary Ann Elizabeth was born a Smith, and sure enough, there are three Mary Ann Elizabeth Smith births registered in 1855/6, two in St Pancras and one in Stepney. Ratcliff was in Stepney at that time.
I don't know where the Henry Roach the butcher comes from, unless it was just an assumed father for respectability's sake. The Henry who Mary Ann appears to be living as a sister with remains a bootmaker.
If no better story can be found and this was my family, I would look into this further, possibly buy the birth cert and see where it leads.
