Bally Sports has said they are launching a standalone service. However, notice that's future tense. It hasn't happened.
The wording about needing cable is misleading. You need a TV provider package that includes Bally Regional Sports. That is often cable, but can include a live streaming service that carries Bally Regional Sports. The good news is there is one. The bad news is who it is, based on your other comments.
Currently, the only service that offers Bally regional sports networks is DirecTV Stream Choice package, which is $90/month, $80/month for the first three months. All of the other live streaming services dropped Fox Sports regional networks, which were sold and rebranded as Bally. DirecTV Stream (formerly AT&T TV, formerly DirecTV Now) is the only service to carry them.
You could drop Hulu+Live TV (that's the service you have; Hulu is part of that service, the $7 part) and switch to DirecTV Stream. That would give you many of the same channels you have, but a few additional ones. Here's a comparison of some services from Cord Cutters News: https://www.cordcuttersnews.com/live-tv-streaming-comparison/
As of now, that's your options for watching Bally Sports: go back to cable, switch to DirecTV Stream. Until the Bally Sports standalone service launches ... in the future.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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