Roku streaming stick shows old nickname

Just ran into the same issue. An old device name was showing on my iPhone and iPad when Screen Mirroring (AirPlay) to my TCL Roku TV. Checked the device list in the Roku app and website. The device, there, was showing the correct current name. So, I changed one letter of the device name in the device list in the Roku app, saved it, then went to the iDevices and turned off Wifi. While Wifi was off, I went into the Control Center and tapped on Screen Mirroring so it would clear the list (since it wasn’t connected to Wifi and wouldn’t find anything). After a few seconds, I turned Wifi back on and tried Screen Mirroring again. This time, it found the device with the new name (with the single letter changed). So, I repeated the process, changing that one letter for the device name back to what it should’ve been and all was fixed.