It is beyond me why Roud left,out of the thoughtful side of the revival...

This quote from the book says what he was concerned with:

"So, this is a book of social history, covering folk song in England from the sixteenth century to about 1950. It is not really concerned with the folk music which developed through the post-war Folk Revival, when everything changed dramatically nor is it about now, but about what used to be..."

So, his book is about folk music before the 1950s revival. Though he does include some quotes from revivalists, he was not concerned with them but who and what came before.

He also says early on that the definition of folk music he is using is basically the 1954 definition though he does suggest replacing the reference to Music Hall songs with one to commercial popular song generally which seems reasonable to me.

I do get the impression, Jim Carroll that you've not properly read his book but have skimmed through and selected the bits that suited your agenda. Now, that may not be correct but surely in a book like this you need to be sure exactly what the author is concerned with, what he has said he is discussing. Without that, you cannot fairly criticise him.