Roku for Android Version 184.108.40.2069945 on Samsung Note10+ on Android 10. Rokus are a Roku Stick 3600X v9.3.0:4170 and Roku 3930X v9.3.0:4170.
New remote app is an improvement, but if I am away from the app for "a length of time" (15 minutes or more?) and return to the app, the app remain responsive, but the actions do not happen on the connected Roku. Even the remote listening responds, shows the pop-up, but the audio remains on the TV.
If I kill the app and relaunch it opens and is again responsive and connected to the previously selected Roku, and now the functions apply to the Roku.
We are most commonly in the YouTube app, so I cannot swear this happens with other apps, but it _does_ happen when the Roku has been left on the home screen.
I will try this on my other phone, an older LG V20 on Android 9 and report back here if my experience is different.