The Roku app on your phone should find all Roku devices connected to the same network as the phone.
When you go to the tvs with the "missing" Rokus, do those Rokus show as being connected to the net? The same net? Settings > Network > About
- Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
- Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T
- TCL Roku TV 43S425/C107X, Ser X000001R60KV, wifi