Even if had the app, when open it all it says is wait for Nov 12 to start streaming. So wait for tomorrow.
I read in another forum that they aren't rolling the channel out until later today. Why? Who knows...
Here's the chat that the person had with support. No idea what Time Zone they are referring to. The time stamp is in UTC, and it's past 9PM UTC now. That link to the channel still isn't live yet.
Chat started: 2019-11-11 06:02 PM UTC
(06:02:51 PM) Xxxxxxx: When will the Disney+ app be available for my Ultra (2018). I searched again this morning and could not find it.
(06:06:39 PM) *** Sarah joined the chat ***
(06:06:49 PM) Sarah: Hi Xxxxxxx!
(06:06:58 PM) Sarah: Thank you for contacting Roku Support!
(06:07:55 PM) Xxxxxxx: Hi
(06:08:14 PM) Xxxxxxx: When will the Disney+ app be available for my Ultra (2018). I searched again this morning and could not find it.
(06:11:28 PM) Xxxxxxx: hello, anyone there?
(06:11:53 PM) Sarah: Yes, we are still connected.
(06:12:01 PM) Sarah: I am checking it for you.
(06:12:07 PM) Xxxxxxx: THX
(06:14:42 PM) Sarah: Thank you for the patience.
(06:14:52 PM) Xxxxxxx: NP
(06:14:56 PM) Sarah: May I know the device model number?
(06:15:07 PM) Xxxxxxx: 2018 Ultra
(06:15:39 PM) Xxxxxxx: 4660X
(06:17:41 PM) Sarah: Alright.
It can take up to 24 hours for the channel to appear in search on devices. You can add the channel from the direct web channelstore link here: https://channelstore.roku.com/details/291097
(06:18:14 PM) Xxxxxxx: that link doesnt work for me
(06:18:57 PM) Xxxxxxx: says page not found
(06:24:52 PM) Xxxxxxx: still there ?
(06:27:18 PM) Sarah: Yes, we are still connected.
I request you to try this channel launch at 9 pm.
(06:28:04 PM) Xxxxxxx: Really? You're going to make everyone wait until the content goes live and have everyone try to download the app at the same time?
(06:32:29 PM) Sarah: We request you to wait until the 9 pm, Xxxxxxx.
(06:33:07 PM) Xxxxxxx: OK
Problem is, Midnight in what time zone? Someone on the AVS Forum had a chat with Roku Support, and was told it would be available at 9 PM. The person was located in Texas, but 9 PM there isn't Midnight Eastern, and is only 7 PM Pacific. So we really don't know exactly when the channel will be available.
From the above:
"Here are the times we can expect to see all that Disney goodness! 3 am PST, 4 am MST, 5 am, CST, and 6 am EST. So for those of us on the west coast that’s 3 am with a much more manageable 6 am on the east coast. Additionally, if you’ve been frantically looking to downlad the app on your TV and smart device, don’t fret, the app won’t be availabe till launch time. "
There are unsubstantiated rumors that we could see the streaming service launch at 12 am-midnight (11/12/2019).
Countdown to launch on the Disney+ site confirms this info.