I use a Netgear extender and my Rokus can connect to it without problems. I have the extender configured to use a different web name (SSID) rather than duplicating that of the main router ("-ext" added to SSID), if that makes any difference.
- 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