@Jeff26
If Airplay doesn't work for your needs https://support.roku.com/article/360057488733, then you can try out additional casting apps available from the Apple Store.
I use(d) Web Video Caster when I had an Apple phone and continue to use it on my Android devices. There are others as well that work well with Roku. https://channelstore.roku.com/en-gb/search/web+video+caster Basically you install Web Video Caster (WVC) app on your mobile device and the WVC receiver channel/app on your Roku device. Allows many different casting options, so may work for your needs.
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Because these streaming devices are reasonably priced. some streamers have different HDMI devices (Roku, Fire, Chromecast, Android) attached to their TVs so they can just switch between devices and features as necessary and needed. Until Roku decides to license Chromecast ability, options currently are to purchase an additional Chromecast dongle or to just try and add the additional casting feature yourself via mobile app, like WVC and others.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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