Hi
From the records I have seen Sarah Rocke (nee Jennings) and Andrew Rocke called their first daughter Mary Ellen second daughter Sarah and their third child (a boy) Samuel Matthew possibly after the parents Mary and Samuel and Sarah herself which tends to suggest the Sarah Jennings from St Ives is the correct one as the name Mary does not appear in the "Sea Queen" Jennings family from Clapham, Surrey. This is only supposition and not factual proof though.
It was Sarah Elizabeth Jennings who migrated on The "Sea Queen" and I have not seen Sarah Rocke referred to as Sarah Elizabeth Rocke except in this online public tree.
I'm puzzled by this change of name in by deedpoll from 'Rocci'. From my memory I think this was supposed to have happened in 1952. Andrew Rocke died in 1903 and previous to Rocke the surname used was Roche.
jackhammer