Audio latency can have several sources/causes, ergo several fixes may be used. There is no "one fix" because there is no "one cause".
1) App/content caused:
A) Pause, Play again - try again
B) RW, Play again - try again
C) Reload content/stream - try again
D) Reload app - try again
2) Roku configuration caused:
A) Switch Settings/Audio/HDMI = Auto passthrough (if available - model specific) - try again
B) Switch Settings/Audio/HDMI = PCM-Stereo - try again
C) Disable all Volume modes/Sound Settings: During playback press Options (*)/Sound Mode=off or Volume Mode=off - try again
D) Restart Roku: Settings/System/System restart/Restart - try again
3) HDMI CEC caused:
The most effective "fix" is to power everything (Roku/TV/AVR/Soundbar/etc) off completely and unplug them all from AC for 5-10 minutes, then power them on in the following order:
A) AVR/Soundbar fully on.
B) TV fully on.
C) Devices connected to AVR/Soundbar fully on.
D) Devices connected to TV fully on.
4) TV/AVR/other device configuration caused:
A) Go into the Audio and/or CEC settings of your TV/Display/Projector/AVR/Soundbar
B) Disable/set = 0 all Audio Latency/Lip Sync handling - try again
C) Enable/set = desired amount Audio Latency/Lip Sync handling (enable Bypass if available) - try again
D) Unplug all equipment from AC power for 5-10 minutes after making changes - try again