The UI on the Premiere is really slow. It can be very frustrating at times. The Romaio uses basically the same UI, with a few improvements, but the hardware is fast enough to make it usable.
The other major differences are in the apps. The Roamio uses a new apps platform. Netflix and YouTube have already been updated and others are on the way. Going forward it is likely we will see new apps released only for the new platform leaving Premiere units out in the cold.
That being said if you have the patients for the UI and don't care about apps then you mig be OK with a Premiere.
Developer for VideoReDo