You can add or change a specific function to the remote by Logging into the “My Harmony” app, naming the function, then dragging & dropping it to an unused button on the remote. I tested this, using the blank / colored buttons, worked well for me, because I’m not smart enough to program into it.
I’m going to set this up with my Roku as well. You’re right on with the pricing, you can get it at Best Buy, Amazon or Sams / Walmart for $40 but it looks and seems like a much more expensive remote.