For free the new Adult swim app offers 24/7 marathons of many popular adult swim shows. (Typically older episodes from shows like Rick and Morty, Eric Andre, and more.) You can also find 24/7 streams that mix together different Adult Swim shows and Anime from Toonami. You will also find a handful of episodes from many Adult Swim shows streaming for free.
Now if you log in with a supported provider like PlayStation Vue you will get even more content but there is an impressive lineup of content here for free for cord cutters.
Right now the Adult Swim app includes support for Chromecast from iOS and Android allowing you to cast your shows to your TV. You can also use AirPlay on iOS to cast your shows to your Apple TV.
Here is the description from the Roku Channel:
Adult Swim floods your TV with marathons of your favorite shows, a daily Live Stream of interactive programs, featured episodes spanning our entire history, plus our nightly on-air simulcast.
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