I've read a number of threads on this topic and succeeded in confusing myself. I have a Roku Streaming Stick+. I want to mirror my android phone. From the threads, it appears the easiest method is buying a Chromecast Dongle.
Is that correct? Is there a monthly fee?
Can I mirror straight from phone to TV/Roku? Is so, using which phone app? I've tried Chromecast, which nags me to sign up for a monthly fee, and Google Home.
You 'may' be able to mirror an android phone with miracast, depending on the phone. However it is generally an awkward way to access content. If the content is 'on' the phone, like photos, music, or video files, the roku app can send them. If the content is coming from the internet, you can probably find a native roku app/channel to view it directly. A few applications like YouTube and Netflix have their own casting protocol and will work to let the phone tell the roku what to play.
There are a confusing number of choices... First, if your phone has miracast, you can just mirror it, so investigate that first - whether you phone supports it and how to activate it.
Next, there are better ways to do most things unless you want to display your text screens or something else completely unique to your phone.
There is a roku app that you can install on your phone that works as a remote control but can also send content from your phone to the roku. This isn't mirroring, but is better for music, photos, and video files that are on your phone.
If you intend to play content from the internet on your phone and mirror it to the TV, it is generally better to find a native roku app/channel that will play it directly. Since you mention youtube, yes roku has a native youtube channel and you can either select the content with the remote or use your phone to search, then cast a video to the TV. If you touch the little screen-looking cast icon in the phone youtube app you should see the roku as a possible destination. Netflix will do this too, but most others won't. For example if you have Amazon video you have to select it with the roku remote, but you could use the phone to add something to the 'watch next' list to make it easy to find.
YT and NF support a casting protocol called DIAL (they also support GoogleCast/ChromeCast, but that isnt relevant for devices that dont have ChromeCast support).
Mirroring is not casting. Casting is not mirroring.
AirPlay2=mirroring & casting
GoogleCast/ChromeCast= mirroring & casting
Again, if you want to mirror to your Roku, since you are using an Android device, you'll need to use the Miracast function (screen sharing/screen mirroring) of your unknown manufacturer unknown model phone.