From what I can find out, the harmony 650 should at least partially work with the roku ultra (since it has IR) , is that true?
But how well does it work? Does the harmony 650 have a button that corresponds to the home button on the roku? And does it have one that corresponds to the arrow button to the left of the home button?
The buttons will work however you program them to work. For instance, if you want "Menu" to act as the Home button, it will if you tell it to.
The Harmony interface should allow you to program any button to any function.
Yes, you can program a button to switch the input on your TV to the Roku input and have it perform any number of button presses at that time. The manual tells how to do all that.
Why don't you download a copy of the manual and see if what all it will do will work for you? A search for "harmony 650 remote" will locate it.
Is there a reason you want a universal remote instead of the Roku Ultra remote? The Ultra remote controls the TV power and volume (but not the volume of a sound system). If you're looking for a single remote to do TV, Roku, and other stuff, it should do the job.
The Harmony 650 is extremely programmable, and I believe it might contain a Roku configuration, or be able to download one. I have two, but it's been so long since I've used them they aren't even programmed for any of my existing equipment. The wife would rather stick with the standard remotes, because she's comfortable with the buttons now. She gets a little testy when I add new equipment.