Why do I need an additional player device if I have a Roon nucleus and a dac?

I'm really not sure what you are asking.

If you are asking "do I need a streamer if I already have Roon and a DAC?" then no, you do not.

Actually there is no question. Just some unintelligible statements.

A Roon Nucleus IS an expensive streamer. But you know that.

Your Roon Nucleus can serve the function of feeding directly to the Chord as long as it’s placed close enough to connect with a quality USB cable. You would need an additional player (render) only if you want to place the Nucleus away from your equipment and have the music from the nucleus traveling on you network. The Chord TT2 does not have an Ethernet input so another unit would be required to receive the Ethernet or WiFi signal and convert it to USB for input to the Chord.  You may need something like an iPad for control of the nucleus no matter where it is placed.  

If you wish to place a Nucleus in another room you can use a raspberry pi4 running Ropiee to connect to the DAC. It acts as a bridge. 

Thanks all and especially drrsutliff.  Streaming equipment can be abit challenging to understand, and it don’t need to be.  So easy to make a purchase mistake, etc. 

Two scenarios where you would need a separate streamer

1 is if you wanted to use a service that wasn't supported by your Nucleus (Spotify, Amazon, Pandora) and did not want to connect a PC to your DAC.  As long as you are using your library and Tidal or Qobuz you are good. 

2. The one other scenario (and I face this) is if you can get an ethernet connection close to your system.  My ethernet is 20' away and in a closet and adding a hot spot has proven challenging.  Unfortunately the streamer I chose is not a proper Roon endpoint at the moment (Chord 2Go) and I am stuck connecting to it via airplay.  I am irritated with Chord at the moment (and Roon).  There was no need to implement this certified endpoint restriction in the middle of COVID 19.  

Thanks verdantaudio,
great info.

i will likely get the nucleus.
my Ethernet occurs by splitting the incoming tv cable, supports modem and tv.  A hole in floor is how cable comes into room. Also, via router I feed Ethernet to this room and a downstairs room via hole in floor.   

Based on the reviews I have read, I do not consider the Nucleus overly expensive for what you get, and the build quality.  If I ever needed to replace my Antipodes DX I would not hesitate to consider a Nucleus Plus with an internal or external drive.

Regarding, endpoints, the Nucleus can serve as both renderer and endpoint, as can my DX, and that will be great for many listeners.  However, in addition to the reasons given above, the reason I use a separate endpoint is sound quality.   I use Ethernet to connect my server to my endpoint and then use I2S to my DAC.  Between my server and endpoint, I use two TP Link optical converters to optically decouple the Ethernet connection.  The end result sounds better to me than running the whole thing through the DX only.

You can for sure use JRivers26, Almarro or others as well as Qabuzz, Roon with your pc .what I do highly recommend and truly an upgrade is the Jcat femto usb card, as well as femto ethernet 
card a world of difference ,for not only uses the best commercial femto clocks but regulators and isolation from the computer noise
from the musical signal .easy to install and a highly recommended.
just see excellent reviews .

A Network Acoustics ENO filter on the Ethernet input of the streamer makes a big improvement too.

It is amazing how many people need a course in manners.
emergingsoul, I understood exactly what you you were trying to say. You also could build a NUC instead of the Nucleus for less than 1/2 the price.

Esoul.  you are understandably a little confused about how the roon stuff comes together.  you are not alone.
This youtube is a great help:  http://https//www.youtube.com/watch?v=-ZVcNx-DlIc&t=7s
John Darko does a very good job of breaking it down in all sorts of configurations.

Thanks for Darko link. Seems he is using roon to connect to streamers.  A way of promoting products he may be getting paid for.

he doesn’t choose to keep it simple by using nucleus connected to a standalone dac.  His setups are abit involved.  I like listening to him but always wonder about independence.

From my experience, it really depends on the DAC you are using, and whether you are willing to pay a premium to get incremental gains.

I initially set up my Roon system with a separate streamer (Bryston BDP-2 with upgraded audio card). At the time I was using a Schitt Yggdrasil, and it sounded best using an AES3 connection (this was before Schiit's latest USB interface, so don't know how that compares).

Earlier this year, I bought a Denafrips Terminator and I found this DAC sounded as good over USB directly from the Roon server (Roon ROCK running on fanless NUC using a linear power supply) as it did through the streamer. 

So basically, for the cost of the Yggdrasil DAC and the streamer, I was able to get a much better DAC (in my opinion) that didn't require the streamer. 

There are all sorts of things you can spend money on to tweak the digital playback chain including streamers, reclockers, master clocks, linear power supplies, upgraded ethernet switches, cables and more cables, etc. Many of these things will make an incremental improvement over a simple Roon server connected via USB to your DAC. But you have to ask yourself 1) is it worth the extra expense and complexity, and 2) is it the best use of your budget?