Update is up to cbc gem to add the channel and develop the channel to roku. So if you want cbc gem you must email cbc and keep asking for cbc gem app for roku. I contacted them directly and we just have to keep at it until they realize there are lots of roku users that want canadian content.
It is not all up to Roku. CBC has to offer it to Roku. I have e-mailed CBC asking for them to put Gem on Roku. Since they have put "CBC TV" on Roku recently, hopefully gem will follow. I watch on Fire Stick, but the user interface with Fire Stick isn't very good. I prefer Roku.