My configuration is shown in this post. Meanwhile, as no one was answering my post, I replaced the SSD with 500GB one using a backup. So, in summary:
Synology DS1513 NAS flac/m4a files → Netgear GS108T switch (dual Gigabit) → Roopie Client, all controlled via Roon on a iMac or iPad. All connections through ethernet, no WiFi at all.