Music Servers/External Drives

You can keep it simple and inexpensive.  A spinning hard drive connected to your Roon server will work just fine.  It is important, however, to have backup copies of your music someplace else.  Any hard drive, be it spinning or SDD can fail.

I rip and/or download new music onto a Mac computer and then copy the music files over my wireless network to a USB hard drive that is attached to my Roon server..  That way I have a backup of my music on the MAC, which is also backed up on the Cloud.

I back up everything to an external SSD Drive. Very simple using the Innuos Sense app. Not that this stuff is hard. 

No matter what drive solution you pick, make sure you have adequate backups. You can get a NAS unit with multiple drives, but even with that you should have an external drive backup that is not connected to your computer or network, in case of a virus or ransomware attack. Another copy should be kept off-site or in the cloud.

I used JRiver to rip all my CDs to FLAC files. They are stored on my desktop PC, but also backed up to a single-drive Buffalo NAS drive. All my streamers (Bluesound) are pointed to the NAS drive. I also have a copy on an external HD (disconnected from anything) and a copy in a cloud backup service.

 In addition, SSD reads data without generating vibration and is supposed to give less electric noise that compromises SQ.

Yes, although  as I understand it, this isn't  an issue if you're only using an HDD for local library storage with Roon (and not as the location where Roon Core is installed).  In Roon's storage settings, you set a path to the device.  Then Roon continually monitors it for new files.  When it finds them, it integrates them into your Roon library. In that scenario, I don't believe Roon goes back to the HDD to read the data for real-time playback (again, assuming Roon Core is not installed to that HDD).

Lanx0003 makes a good point.  If you use an external hard drive, BACK IT UP REGULARLY!!!  They have a tendency to fail with little or no notice.  I keep a clone of my main drive connected to a difference stereo in the house.  I find that the Seagates are the most reliable, but don't risk a catastrophic loss of a curated collection for failing to spend an additional $150 or so on a second hard drive.

SSD with max. data transfer rates over 800 mbps.  This will work much better than 7200 rpm HDD with only 160 mbps in terms of indexing on the first setup or later update.  No moving parts inside SSD makes it less volunerable and hence longer life expectency.  After all, losing data after a long time collection is excruciating.  In addition, SSD reads data without generating vibration and is supposed to give less electric noise that compromises SQ.

Thank you all for your replies and detailed explanations. This is very useful information. 
SW

I recommend using Exact Audio Copy for ripping CDs.  It provides a bit perfect rip and is free shareware.  I don't think that you can rip to ALAC, but conversion between ALAC, FLAC, WAV and many other lossy and lossless formats is easy with DBPowerAmp, which is my favorite conversion software.

I use a Seagate 5 terrabyte hard drive attached to Cambridge Audio N851 Azur for most of my listening and it sounds great.  It provides the flexibility to play all sorts of formats and high resolution files.  I do highly recommend using a good USB connection between the HD and your server/streamer.  I was skeptical, but adding an Audioquest Diamond USB 3.0 cable and an Audioquest Jitterbug between the Seagate and the 851N made the most dramatic difference in sound than any other cable improvement I have made.  The sound immediately became fuller, more present and nuanced in my system.  Good luck!   

Roon makes it very easy to share a variety of locally networked storage devices and make them integrate seamlessly with streaming services (Tidal/Qobuz).

I host my local music library on a headless Mac Mini, my "Jukebox", which I access via Screen Sharing from a MacBook Pro.  Roon continuously monitors a folder on the Mac for updates. I store ripped CDs on the Mac, as well as music files purchased from HD Tracks, Qobuz, or other vendors.  Roon Core runs on a separate, dedicated music server (a sonicTransporter i9), although it also can run on the Mini.  Both the sonicTransporter and the Mini can run certain DSP applications such as HQ Player.

Some audiophiles dislike having a full-function computer in a HiFi system, especially one co-located with the main HiFi components.  I find it very useful and versatile. I don't notice any fan noise. Occasionally a DSP application fails to launch until I respond to a system event (such as an automatic software upgrade process).  Those interrupts can be minimized by turning off (or carefully scheduling) processes such as Time Machine backups.

I also have an SSD inside the sonicTransporter.  Lately I only use it to store a backup copy of music files, and have it disabled in Roon's storage settings.  At any rate, whether you're using a full-function computer, a NAS, an individual USB-attached SSD, etc.,, it does not need to be a device specifically made for audio files.  However, the Bluesound Vault is such a device, which you might want to check out if only to research what's possible.  

Any external drive works fine but spinners need a separate power supply.

Nowadays there is no reason not to use SSDs Smaller, faster and USB bus powered.

I wouldn’t know about Roon but if it only likes DLNA via NAS then that’s another reason to avoid it. I sold my NAS, not looking back.

If the network drops its handshake the NAS disconnects. Phooey.

dbPoweramp is my choice for ripping. Flac all the way. I tried alac but it doesn't sort for shit in Windows. Flac is universal.

I rip to ALAC using free XLD with "max retry"  set to 200.  Recently I used internal Jriver (Media Center 30) ripper and it seems to be fine.  FLAC is more universal, but does not work with ITunes (that I used before) while ALAC is native Apple format.  Both can be easily batch converted.   XLD can be used for that, but FREAC is even more convenient.  FREAC (freac.org) is wonderful free small program for ripping and converting.  I use it for batch converting only to HE ACC for car.  Advantage of ripper over CDP is that it can go over given sector multiple times (unitl proper checksum is obtained) while CDP can only read once (working in real time).  Some rippers do this better than others and knowing number of retries plus getting detailed report (both in XLD) is important.  Any external drive will do but mechanical drives are a bit noisier.  I used them but now I use 1TB SSD with two backups.  Reason for backup is obvious, but second backup is just extra precaution.  For instance computer failure (hardware or software) during backup can make both HD unusable.  In addition I keep one of them outside of my home in case ot theft, fire etc.   I update one at home every 5 or so rips and from time to time I exchange them.  I have so far 1700 CDs ripped occupying 600GB. 

ge a nas roon reconizes nas but not external hd

rip flac and you are good