Dennis, thanks for your help with this Query. I'm certain Adele is not Olivia but very well could be her sister. I see an Adelaide DeRoche age 24 residing with another family in the 1871 Census, Arichat. I cannot a George and Olive DeRoch in the 1871 Census, but do know he existed as he is listed in the 1870 "List of Occupations" Arichat.
http://www.ourroots.ca/e/page.aspx?id=279787
In the little window saying Queens Co., select Richmond and it will give a brief history of Richmond and what is taking place there in 1870. Arichat was a busy shipping port. George shows with the other DeRoches listed in Arichat.
George DeRoche also reported the birth of Elizabeth Mann in 1868, two lines from the birth record of George Walsh. That Elizabeth is the girl residing with John Walsh in the 1881 Census with her mother Harriet.
I see a George De Roch born 1844 in Cape Breton, in the 1881 Census, in Montreal. He could be a son of George De Roch, Arichat.
For your info, Skydot, there are 45 DeRoche and DeRoch in the 1901 Census in Richmond Co. Surely you will have contact with some of them. Best of luck in your search.