In this article, we'll explain how you can use your Roku to mirror your iPhone on your TV screen, without having to purchase an additional dongle or an expensive Apple TV.
Onn. Roku TV: How to AirPlay (Wireless Screen Mirroring) All iPhones, iPads, iPods
You will need to make sure that mirroring is already set up and allowed on your Roku receiver. These instructions apply to all current iOS/iPadOS devices and all current Roku devices that support wireless incoming connections.
On your Roku, go to Settings > System > Screen Mirroring.
In Screen Mirroring mode, make sure the Ask or Always Allow option is selected, indicated by a check mark.