On this Sportsnet Now page, it says SN Now is available on "iPhone, iPad, as well as Android mobile and tablet devices". No mention of Roku or other streaming devices.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X