Let me throw one thing in.
Are both Roku devices going to be using the IR remotes? And, if so, are they located in such a way that when you point the remote at one, it could be confused as being pointed at the other? For example, to adjoining rooms, but layed out in such a way that if the door is open, you can see both Roku boxes?
What I'm saying is one remote can control two boxes at the same time if it can see both boxes at the same time.
I set up my granddaughter's new Roku for her, and did so in the same room as my Roku. Though I had the TV switched to her (temporary) Roku input, my Roku was picking up the remote actions. When I finished hers, mine was all buggered up, because I was actually performing the remote actions on both boxes without realizing it.
Roku 3, Roku 2 XS, Roku XD