I have studied the Rothschilds a lot, as much as I can because it is certainly difficult to get documentation and people would be surprised at all that is hidden from us.
The stuff that IS documented is bad enough, let alone the stuff that isn't!
It is not that it is not documented, but that it is difficult to trace because they have been responsible for erasing the trail, especially in recent times.
While it's not directly about the Rothschilds, they do get a mention, have you read the book The Great Taking by Rogers-Webb?
Yes I read it, although I believe that in reality it is something more complex and comes from much earlier.