Help & troubleshooting for network issues, including connecting your device to your home Wi-Fi network, connecting to public networks, troubleshooting wireless issues & ethernet connections, and optimizing streaming performance.
There are no Roku devices with a cellular modem, so they cannot connect directly to a 4G or 5G connection. When you say hotspot, you are referring to a device that can connect to the cellular network (either a smart phone or a cellular router with a hotspot function), and then anything that supports WiFi connects to the hotspot. So it makes no difference if the hotspot is using 4G or 5G technology.
All the Roku cares about is the WiFi signal the hotspot offers. If the hotspot offers both 2.4 and 5 GHz WiFi, any Roku device will connect. If the hotspot only offers 5 GHz WiFi (I don't know of any that are 5 GHz only), then only the Roku Ultra and Streaming Stick Plus will connect. They are the only two current model Roku players with dual band radios.
Dan Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.