My Roamio Basic 4-tuner (w/ CableCard, not the OTA) had the dreaded flashing green and blue lights. It was dead in the water. The good news is I read that I should try a new Power Supply. The better news is that I found a generic AC Adapter with the same tech specs (as the Tivo-issued Power Supply) and now everything works perfectly. I believe the OTA has the same power supply as my Basic.
Note the Tivo Roamio Basic/OTA replacement Power Supply from Weaknees is $39.99. This generic one I am now using was $10.98 on Amazon.