First off, I’d post in the support area. I believe Apple made changes to the way iTunes works in that you have to generate an XML file now.
Recent versions of iTunes do not create the XML file by default, so you will need to ensure the file is generated by checking this screen and making sure the Share iTunes Library XML option is checked.
From https://kb.roonlabs.com/iTunes
In order for Roon’s @support team to better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so they can have a clear understanding of how your devices are communicating.