For example, I’ve got Mosaic’s The Complete Blue Note Recordings of Larry Young which includes Grant Green’s Street of Dreams in its entirety - which I also have. Out of 4 tracks, it only finds 2 in common.
Same with Grand Green’s I want to Hold your hand - here 4 out of 6 are identified.
Any idea why this is so? What should I be looking for in the metadata to get Roon to identify the tracks as being the same?
It’s a little complicated, but a common normalized track title and a common composer are pre-requisites for “composition munging” in the Cloud.
In the Roon core, we also perform munging if we have more information than we did in the Cloud; for example, your track tags have composer information and/or you have added a composer via a Roon edit.
“Munging” is an official term by the way. 
There is also a bug, meaning that some works mysteriously don’t get attached to their composers.
If I add composers, it generally works well.
Chris, not very helpful. Yes of course it works “generally” very well. But there is an intermittent problem which I have reported some time ago and which causes the whole thing overall not to work as designed.
I hit Roon very hard with heavy, high level usage, and make serious demands of it, which is why I find this kind of problem disruptive…
Just my experience and not designed to be unhelpful in any way.
Fair enough! Lucky you not to have been troubled by the problem!