sfx2000
Part of the Furniture
It's likely that you're seeing a wifi-direct channel used for the Roku's remote control or screen sharing. Typically, wifi-direct uses names like "DIRECT-roku-xxxxx". It can be ignored.
I agree - this is the wifi direct SSID broadcast from the Roku to share content/media from another source (PC, Mobile Phone, etc).
It's harmless, it is just a beacon unless it's being used, and it's secured, so not a thing to worry about there (the Roku wouldn't route to the LAN from that interface anyways).