After a little research, Rokus with 5GHz don't support the DFS (dynamic frequency selection) channels (52, 56, 60, 64, 100, 104, 108, 112, 116, 132, and 136).
DFS channels are shared with other uses such as weather radar. Routers supporting these channels must be able to detect such licensed use in your vicinity and automatically switch you to another channel. Some router manufacturers don't include this capability and so don't support those channels at all.
That leaves the following non-DFS channels that Rokus and virtually all 5GHz routers DO support: 36, 40, 44, 48, 149, 153, 157, and 161.
Reference: https://superuser.com/questions/692835/ ... nel-to-use