I've posted a few times recently to cover various questions of mine. Just to preface again, I'm a TiVo old-timer who switched to Windows Media Center a couple of years ago and am thinking about coming back.
I used to have a dual TiVo HD (Series 3) setup in the house and my recollection was that I could transfer shows from one box to another. If memory serves, I believe that if I was in my bedroom, I would go into that TiVo's main menu / list and the other TiVo would be listed (e.g., labeled as "Living Room") and then I could select it and see what shows were recorded on it.
I'm wondering with newer Roamio's and UI changes if TiVO has now (or now allows you to) more seamlessly merged the shows that are spread across multiple Roamio's into a single list, so that I wouldn't even need to know/care which TiVo the shows are actually stored on.
I can see pros/cons to both approaches. For example, it might not be a bad idea to designate one TiVo for my wife and her shows, and the other for mine (That raises another question: Even with just one Roamio, can I categorize shows as being my shows versus my wife's shows?). So, ideally, the TiVo would allow both approaches and would allow a very fast way to switch between a single seamless list and a list grouped by device/person.
Ideally it would also allow all tuners to be pooled, so that if I could use one TiVo for most/all of my scheduling, and it would make use of the 2nd TiVo's available tuners.