The story on the internet is that Ireland does not allow foreigners to adopt from Ireland. Roberts and wife arranged for two pregnant Irish woman to travel to a Latin American nation. When they gave birth the babies were brought to America and adopted.
Thus the adoption papers said adopted from (say) Argentina. Do a search and you will find this on the internet.
https://underneaththeirrobes.blogs.com/main/2005/08/the_roberts_ado.html
If Wales, the UK requires a one year residency for adoption. Not sure if that was case years ago when Roberts kids were adopted.