Which Roku device (to include model number)?
Do you know if you're connected to your 2.4 GHz network with the Roku? Or is it connected to the 5 GHz network?
Is your iPhone connected to the same network (2.4 GHz/5 GHz)?
Also, does your iPhone have WiFi Assist enabled? Settings > Cellular > [way down at the bottom] Wi-Fi Assist
If so, disable that. What that does is if your iPhone thinks your WiFi connection isn't strong, it'll switch to cellular. The description is there on the iPhone. Anyway, if your phone switches to cellular, it won't see anything on your network. Make sure that's off.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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