Roku Express not connecting to Netgear AC1200

> [...] Could not determine problem [...]

   Doing what?  Try harder?

> [...] so I reset Roku to factory reset. [...]

   Because you determined that the R6120 was working correctly?  What?
You didn't?  Perhaps you should.

   In a system with two boxes, the problem is usually with one of those
boxes.  If the Roku box shows some wireless network as available, but
not the one from the R6120, then I might start to worry about the R6120.
What else works with the R6120?

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual.  Read.  Look for the LED
descriptions and "Troubleshoot".  Pay particular attention to the "WiFi
LED".