Apparently, your application is still waiting assignment, examination, and approval, so technically no trademark exists/awarded.
I see your concern here, but that other other channel has a different name (Black Lives Matter Tv), a different logo, different content, is abbreviated BLMTV in its thumbnail, channel has been in place since 10/2020 where yours is different logo and says BLM TV, and channel placed 10/2022 and recently filed for trademark 10/4/2022 for the mark BLM TV - THE REVOLUTION WILL BE STREAMED.
Your initial posting seemed to indicate they either stole/duplicated your channel or took the name of your channel. Until your application for exclusive use is approved, don't really see what Roku is supposed to do. (But of course, it will be up to them).
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102