Similar interference problem here. I picked up a new Roamio Pro a couple weeks ago and could not get the new RF remote (Slide Pro) to pair. I spent a good hour on the phone with a Tivo CSR trying all kinds of different codes and sequences to no avail. Tivo shipped a replacement Slide Pro remote and that also failed to pair.
Previously I had tried shutting down most of the RF devices in the house, but was still unsuccessful with pairing. Like most, we have a ton of RF devices in the house (WiFi, bluetooth, wifi extenders, cordless phones, cell phones, game systems, etc). Rather than kill every RF device in the house, I decided to remove the Roamio from the house. I took the Roamio out to the shed (no, not the wood shed) out back, closed the metal clad doors and booted the Tivo. This allowed the Slide Pro to pair with the Roamio!
I was then able to bring the Roamio back into the house, install it in the AV center, and the remote still worked in RF mode.
I haven’t been able to determine what frequency or transmission technology the Roamio RF remotes use, so I don’t know what was causing the interference. All I know is that it was something in the house. If anybody knows the RF frequency/technology used by the remote I would really like to know.
So I would suggest turning all other RF gear off, or moving the Tivo to an area with less RF if you are having troubles pairing your remote in RF mode.