Where does the DAC go?

Noob to digital audio.

I have a ROKU M1001 hardwired to my ethernet connection and for output I am splitting the 1/8" mini into two RCAs which go into the amp input. Streaming radio only, no computer involved.

Where, if anywhere, would a DAC go into this setup?
The internal DAC in a ROKU is like the one in an iPod in that it's cheap. If you're using any streaming media player for music into a hi-fi, then you will improve the sound by plugging the player into a half-decent external DAC.

The player requires a digital output to do this.

Then the DACs analog outputs connect to an input in your hi-fi.

I use a Cambridge DACMagic for my Apple TV and I'm quite happy with it. It goes for about $400.
1. You do not need another DAC.
2. It is possible that inserting one might improve the sound quality but......................

3. Until you tell us what the rest of the system is and what audio streams you are listening to, it is impossible to say whether adding a "decent" or "half-decent" DAC is going to make an improvement.

Gadgets for the sake of gadgets only make for clutter. There is a tendency on these forums for there to be recommendations based on the poster's personal history that do not necessarily apply generally. Everyone's situation is different.

Kal's words ring true to me. Well, I'd expand on 1. and say that you really don't "need" any of this stuff. I think that goes without saying and none of us would be here if we didn't "want" something more. That said, there are plenty of threads on budget DACs to search out. The good news is that digital tech has advanced at such a rate that you can get a lot more for your $ than say, 10 years ago. The answer to your question is, of course, relative to what you consider decent, and how well your system will respond to your "better" version. I could only guess that an audible improvement on a resolving system is easily in the $500 range and even less, though I don't know the threshold where your investment will not meet with your personal expectations. Plenty available in the 400-600 range that will likely best the DAC in the ROKU (again, an educated guess on my part). Candidates in that range that I'd recommend: PS Audio DLIII and the MHDT Labs Paradisea +. There are others, for sure. But per the sage advice from Kal, consider the rest of your system (just how well it might bring out the differences you are seeking) as well as your own expectations of what "better" is worth in dollars invested.