Welcome to Rootschat. Three children of Henry McShane and Rose Forbes are listed in IGI (
www.familysearch.org):
Catharine born 2 Oct.1864 Lurgan district, Co. Armagh
John born 16 Apr.1869 Co. Armagh
Rose 29 Jan.1873 Dalziel, Lanarkshire, Scotland
John's birth certificate will give you an exact place of birth.
If this is the correct family and they did move to Scotland then Rose's birth certificate should show the date and place of her parents' marriage (Scottish certificates show those details but Irish ones do not). You can view a scanned image of the certificate on Scotland's People website (see
www.scotlandspeople.gov.uk for what information is on Scottish certificates and how to purchase credits to view them. Scottish census records up to 1901 census are also there).