Unfortunately Roon aren’t very green (no integrated WOL) and encourage a leave-it-on 24/7 mentality.
It depends what you are using for an endpoint. It’s easy to configure a Raspberry Pi to send a WOL command to your server. For my main Trinnov system, I have an a Pi whose sole job is to send a WOL command when the system starts and then shut itself down.
Edit: there are also numerous iOS and Android Apps that can be configured to send a WOL command. It’s just less convenient and less ‘other system user’ friendly.