ROON help needed

Make sure Roon is working well from your PC, that is: as Control, Core, and Output. I am assuming this is how you have your PC set up; you mention you are using a PC (i.e. not a Mac).

Uninstall the Roon App from your iPhone. Reinstall it. If you have enabled the device (your iPhone) on the main settings page within Roon (on your PC) and the iPhone app still doesn't lock in, then contact Roon.

I don't think there should be any cross platform issues. I believe Roon Remote works fine on my wife's iPhone, while I am PC and Android based.

+1  :)

I feel your pain. 

It's not easy when you first move from Tidal to Roon. Roon does load a whole pile of albums, and I think you will appreciate that feature later.

Like any software, there is a learning curve. Roon gets frustrating when one runs into problems. One more or less needs to familiarize themselves with the software and the support forum. Good news is that Roon itself or another member usually come to the rescue.

Roon 'IS' and offers so Much More than Tidal ... which I believe you will appreciate as you get more comfortable with it. If you want to keep things very simple and straightforward, then it may be better to stick with Tidal direct.

You have 60 days to figure it out. You can always come back to it, in the future if you find it too much at present.

I'll likely move to a lifetime membership once my current yearly membership runs out. So I'm not coming at this from an 'anti' Roon perspective.

Do you have a local audio buddy that is Roon savvy? Or one that can get on the phone and walk you through it? Might be very helpful to do so.

I love Roon, but if one isn't that far into computer based audio, and doesn't want the frustration, then I recommend staying with Tidal. It will save you the subscription fees as well as on the 'components' you will need to add to truly elevate and optimize sound quality. There are some less expensive options; but many will quietly add up. : ) 

If you are committed to going down that path, you will be rewarded and Roon will be a an integral part of your system and listening experience.

For clarification: My Enabled Network Output Device is my Sonore Signature Rendu SE. In my case, I would not want to Enable my Google Pixel XL.

I'm guessing that your PC is your Output Device. Therefore your iPhone should not be Enabled. In any case, I believe that Apple iOS is Control only (and cannot Output). But I may be wrong. I'm not in that ecosystem.

On your PC:

Settings > Audio > Networked Devices

First see if your iPhone is listed there.

If it is not, hit the refresh 'Circular Arrow"

If it still does not show, Contact Roon.

If it does show, this area allows you to select it as your default Output Device. I have Not Enabled my Google Pixel XL.

 See how the remote works for you via the iPhone first (that is Do Not Enable it).

Try this approach first.