The don't list a Roku app here: (see devices down at the bottom of the page.)
Why? You'd have to ask them. And/or inform them that you'd like one. Pretty much everything you see in the Roku channel store that does NOT have Roku in its name is created by the content provider.
There is a complete list of supported devices here. (no Roku)
If you don't want to use another device, or use the website to either stream via HDMI or cast the content to your Roku or directly to your TV, there appears to be an option to use Sportsnet through Prime Video.
https://support.sportsnetplus.ca/hc/en-gb/articles/19476724881682-Sportsnet-on-Prime-Video
Thank you. That worked (using Prime) however it appears I have to pay for that service on top of my Sportsnet+ direct subscription . Guess I have to figure that one out.