Roon can be used with Dirac AU plugins, I’ve configured Roon to use them in their current beta DL 1.x version and used them with success.
(the upcoming Dirac Live 2.0 will feature AU and VST plugins as well)
As you can see in the image linked here: http://diracdocs.com/Roon&Dirac.png
one can use Audio Hijack so that the music stream from Roon is routed to the Dirac plugin first and from that to the DAC, or any output device.
(by the way Audio Hijack can be used for a number of other purposes)
One has to drag the Application icon from the menu on the right and then click it in order to select Roon so that audio from Roon will be captured
Then the Audio Units icon has to be dragged after the first icon and they will be automatically connected, the icon has to be clicked and Dirac plugin selected.
Last the output Device icon… again it will be automatically connected defining the path and the output device of choice has to be selected
Audio Hijack demo is available here: https://rogueamoeba.com/audiohijack/
Flavio