Log into Tidal via Web. Make sure you are using the same username in Tidal and Roon. Go to Playlist and select the heart (Added).
When Roon syncs with Tidal the playlist will show up.
A faster way to have the Playlist show up is: Settings>Services>Select Edit next to Tidal>click Sync library now.
Once this is done the playlist will show up in Roon.