I went through those steps on both my Hitachi Roku TV and my Roku 2 device. The audio/video sync problem on live TV persists even after removing the Paramount + channel app, resetting the Roku, then re-loading Paramount +. For the record these are the device/build numbers:
Hitachi Roku TV 5510X, Hitachi model 50R5, software version 10.0.0, build 4195-32
Roku 2 model 4210X, software version 10.0.0, build 4195-04
Paramount + version 5.2, build 20210421 (same on both Roku devices).
This problem began early May, still not fixed. Paramount + either not aware or don't care their app has this incompatibility with Roku. Not sure what to do next as Paramount + not responsive.