So the mx-900 will never control your roku stick, which wifi only, where the mx-900 only controls IR only devices. Upgrade the 3600 stck to something like express 4k+, which does accept IR commands and so your mx-900 will control it. If you want universal remote to control a roku, NEVER get a stick!!

Myself, I just bought two newest Roku sticks to be released, the 3820 & 3821, because I don't use universal remotes anymore, just the roku remotes. :)