A preview is not a selection
Roku’s screen-reader guide says navigating among speech rates plays a sample, but OK selects the desired rate. A viewer can therefore hear a faster or slower example and leave without having confirmed the new preference.
This explains an apparent reset that may actually be an incomplete selection. Check the current rate before assuming the device discarded accessibility settings.
Use a small confirmation task
Open Accessibility, Screen reader and inspect Speech rate. Listen to the choices, press OK on the intended rate and navigate through a short familiar screen. The ordinary menu is a more useful check than the sample alone.
Let the intended viewer decide whether the pace leaves enough time to understand labels. A faster rate can help one person while making an unfamiliar catalogue harder for another.
Preserve the chosen behavior
Return to another system screen and confirm the rate remains comfortable. If the behavior differs only inside one app, report that boundary separately from the system preference.
Keep a short household note of the selected rate and activation shortcut. This is a recoverable accessibility preference, not a reason to factory-reset a working viewing setup.
Questions answered
Does hearing a sample mean the rate is saved?
Roku says OK is required to select it.
Should the fastest option always be used?
No. Choose a rate the viewer can use reliably on the actual task.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.