FWIW, I just tried turning on Hotspot on iPhone 4 and iPhone 5 models, running under Verizon. Roku would usually not recognize them; that is, neither network was shown under Settings > Network > Wireless. A rescan would often show the iPhone 5 network briefly, but the wireless screen would refresh within a second, and the iPHone Hotspot would no longer show. The iPhone 4 Hotspot would sometimes show, and would often remain showing longer than the iPhone 5 Hotspot.
Odd, he said.
Roku 3, Roku 2 XS, Roku XD