If the Mac goes to sleep mode, it wouldn’t have an active network connection and Roon Remotes would not be able to connect.
There are certain apps that support Wake-On-LAN (WOL for short), but Roon does not support this capability at the present time.
We have a feature request regarding this capability, and you can certainly provide feedback towards this feature there, but I suggest that you use a 3rd party app to perform WOL in the interim.