The newest release (2.x) of Roon looks for an Internet connection and won’t run reliably without it. You can verify that by checking the Roon forum, where you will find a minority of users up in arms about that. It doesn’t matter enough to me for me to have an opinion.
Also, that is documented on this page. Those who say it should work are, I'm sorry to say, ill informed.
If you are thinking of disconnecting, Roon would not be a good choice, especially a lifetime subscription. Something like JRiver would be better.