Ok.....best bet is to search the Rhodesian Death Registers to get a Death Notice, that generally lists children (not always as the section is sometimes blank...but has been very useful to me as it often even shows married name of daughters) - have a look at my post to George on this thread: "Zimbabwe Death Registers 1890-1977". It describes how to access the Rhodesian Death Indexes and Death Registers.I have viewed the index and there is no death for a Jean Robertson shown. There are however 7 James Robertsons.The registers are avalable up to 1976. If death is after that I'm afraid its a black hole - I have in the past found the only way to locate documents is to go to the registry in Harare and that requires a LOT of patience and generally a lot of $$$.
Let me know how you get on - if you cant use the info on my other post to help let me know and I will go thru all of the James Robertsons for you....