Is it recommendable to publish the same videos to all of our ConnectedTV Apps?

Yes, it is totally fine to use the same content on all your publishing outlets. You are reaching different customers and viewers on each platform, thus growing your viewership beyond just one device. Besides that, if you have the Lightcast Central Subscriber System integrated on all your TV Apps and mobile apps, which allows your subscribers to watch your content on all platforms with the same subscription, and your viewers are watching a video on Roku for instance and want to continue watching it on their mobile device, the same media content should be delivered to all your publishing properties. This is true also without the Lightcast Central Subscriber System included. 

There is little reason why certain Apps should contain only certain videos. What might be interesting for viewers on Roku, might also be interesting for viewers on FireTV, AppleTV, AndroidTV or your mobile apps or any other publishing property you are publishing to.