Subscriptions purchased through Roku generally need to be viewed through the Roku Channel.
For the most part, if you wish to view a subscription you purchased through Roku, you should be able to login to the Roku Channel on your mobile device (phone/tablet) and then be able to access your subscription content. (https://therokuchannel.roku.com/)
The login credentials for the subscriptions are usually different. As a rule, you cannot just watch the content through the subscription provider's app if you purchased through Roku and vice-versa. In your case, if you pay through Roku, you have to watch through Roku Channel. If you pay Crave directly, you will have to install the Crave Channel/app on your RokuTV or streaming device and login with their credentials. (You will not be able to watch through Roku Channel). Additionally, you would be able to watch on any device simply through the Crave App without accessing the Roku Channel first.
Here is Roku's information regarding this. https://support.roku.com/article/1500008104062
More info can be found on their support pages.
Feel free to post back if you need more clarity.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
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