Henry Rosieur, Charles Cossil and Stephen Wrathall of New Zealand

Harvey Rosieur, who can be reached at harcol(at)clear.net(dot)nz, contributed the following information regarding the Biography of Stephen Wrathall by Richard T. Wrathall:
I have just been reading the Biography of Stephen Wrathall. My family has its New Zealand roots in Mangonui and when I saw the name Wrathall I remembered Phoebe from the general store in Mangonui and other mentions of your family name, and read on. Fascinating reading, particularly when I got to the end of Chapter 13, last paragraph.

There are two items of information that I am hoping other researchers can help me with:
  1. My great-grandfather Henry Rosieur came to New Zealand about 1855. [I believe that] this could be the same person as the Rosieur referred to in the Biography of Stephen Wrathall. [I'm currently researching] the approximate date of Henry Rosieur's voyage, and where in Australia the boat would have left from, the approximate date of the voyage when the ship returned to Australia to pick up supplies and the men named, who included Rosieur and Cossil. The Australian port of destination would also help.
  2. [I also believe that] the Cossil referred to could be Charles Cossil (my great-great grandfather) whose daughter Margaret (Granny, as she was known throughout the district) married Henry Rosieur.
We have been absolutely stumped as to the origins of Henry Rosieur and it seems the Biography of Stephen Wrathall may help to unlock the mystery for us. I would be grateful for any further information which anyone could give me.

Harvey noted that a later chapter of the Biography had additional data on his ancestor Charles Cossil:
Chapter 42 of the Biography reveals how Stephen Wrathall repaid his Foreman Cossil by giving him an area of land on an Island at the head water of Mangonui Harbour and paid the balance of the debt owed to him in cash. That island is Paewhenua Island which remained in the family until 1933 when Thomas Rosieur died and left it to the King family.There can be no doubt that the Rosieur among the men brought back from Australia was Cossil's son-in-law to-be Henry who later married Margaret Cossil (Granny Rosieur, as she later became known, was the first mid-wife in the area). Incidentally it was a Wrathall who attested Thomas' will, as the latter apparently was unable to sign his name and merely made his 'mark'. I hope this little bit of history might be of some interest to you.