I had a RokuTV named "RokuTV" on my network. Recently decided to instead use the Roku Streaming Stick. I reset the RokuTV back to factory defaults and didn't tell it any WiFi info, and instead setup the Streaming Stick, it's named "Roku Streaming Stick+". I've setup my network with separate VLANs as described here: Basically the TV is on a separate VLAN with igmp-proxy on and some holes in the firewall. It was working well, except when I pull up the YouTube app on any of my devices I see two devices to cast to, RokuTV and Roku Streaming Stick+. I can confirm that the RokuTV is unconfigured and in the Unifi Network controller there is no device with that name that has an IP address.
I've restart the app, restarted the phone and it's still there. If I go to another WiFi network the 'RokuTV' entry disappears. Note that if I open the Roku remote app and search for devices, I do NOT see an entry for "RokuTV", only for the Roku Stick.