Koobface is malware that used to infect Macs some time ago, and hasn't been seen in years. It's considered to be extinct. There's absolutely no way that your OS X 10.10 system could be infected with Koobface. Further, it makes no sense whatsoever to say that malware on your Mac could prevent your Roku box from connecting to your wireless network.
I've recently seen another topic (How do I check for Malware or virus on my OSX 10.6.8?) where someone had a very similar report, and said that the Roku representative offered to "clean" her Mac for a fee. Was this similar to your experience? If so, you need to ask some very pointed questions about Roku's tech support and whether you can trust them, and the company they're representing, or not.