I had a similar thought, I would assume the patent is meant to be used defensively to discourage something downstream of Roku from injecting ads.
If Roku wants to display ads, they can already do so if the content originated from their system. If Roku is displaying content originated from an external system, that external system can display their own ads to defeat the detection of pause events. (DirecTV already does this).
If Roku wants to display ads, they can already do so if the content originated from their system. If Roku is displaying content originated from an external system, that external system can display their own ads to defeat the detection of pause events. (DirecTV already does this).