The NowTV Stick is a deliberately cut-down Roku Stick, and this is reflected in its price.
If it had the Roku store, this would cannibalise Roku Stick sales, possibly to the point of extinction.
Neither NowTV nor Roku would find this desirable,
I have a Roku account, and I would like to add my Apple TV account to the Roku channel so that I can stream Apple TV to my Roku stick. Are you saying that the Roku channel does not allow this (it does not appear to, I can't "activate" my roku stick via my account on my laptop), and that an additional app - the Roku store - would be required for this? Thanks.
I have a Roku 3 streaming box, older than the current Roku stick, and I have the Apple TV app, installed from the Roku app store, in my list/stack of 60 to 70 odd apps.
However, you must register your Roku device on the Roku web-site before you can access the Roku app store. And if you're having difficulty registering then, may I suggest, trying a different browser, one without any installed add-ons.
You can’t add an account to a channel - the Roku channel is just another streaming service, like Netflix or YouTube.
What is it you are trying to achieve here?