BallySports+ will be available via the BallySports app on Roku when Diamond Sports Group and Roku come to carriage terms, and not before then (since BS+ has ads, DSG and Roku have to come to an agreement about cuts/injection/insertion/override/etc in order for carriage to occur).
The launch of BallySports+ was in fact a "soft launch", which means a limited initial launch, and the "hard launch" wont be until this fall, so expect an update to the BallySports app supporting BS+ sometime this fall as well (assuming Diamond Sports Group and Roku have come to terms by then).
Can you please clarify the issue you are experiencing? What are the steps to reproduce the issue? Have you already tried contacting the channel provider to see what insight they can provide? Many channels on Roku are developed and maintained by the channel provider themselves.