IME Roku's "Leveling" Volume Mode option is minimal at best, and completely ineffective generally, but YMMV.
The entire "Volume Mode" and/or "Sound Settings" functionality (currently buried/available during playback only) needs a complete overhaul and redesign, starting with putting the controls/indicators of its current state in the main UI under Settings/Audio with everything else audio-control related.
Its one of many RokuOS UX/UI design/implementation failings.
Regardless, the CALM act doesnt apply to streaming services (nor can it ever, streaming isnt within the regulatory purview of the FCC), and relies on self reporting/enforcement of MVPDs to the FCC which again, doesnt audit, and only investigates emerging patterns/trends of consumer complaints.
Effectively, there hasnt been any enforcement of CALM (which cant be applied to streaming without significant Congressional intervention), so relying on the FCC or CALM for regulation of commercial loudness is a dead letter.
The most likely source of effective commercial/ad loudness "regulation" is from the industry itself via new/modified technical standards, but this also relies heavily on self-monitored standards compliance.
Ultimately the solution is working/better "leveling" functionality within RokuOS itself, so pressure needs to be put on them to enhance/change/fix it.
