I'm working on an app that can stream to both Chromecast and Roku devices. I didn't develop this app so I'm still learning the code for it. One of the bugs I'm trying to fix is that there is a volume bar on my Android device playback screen when streaming a video to the Chromecast. I believe this feature is provided to us by the Chromecast libraries. Now on the Roku side, when playing a video, the playback screen has no volume toggle bar. I suspect that this is because its not possible to control volume on a Roku like you do on a Chromecast but I'm not 100% sure. Maybe the developer who made this app (he left for another company) just forgot to include the feature in which case, I'll have to implement it. If Roku doesn't support then it makes sense why there's no volume toggle there and I can just report that to QA.
Side note: I know that the Roku has volume controls on its remote but that only applies when connecting a pair of headphones to the remote so I'm assuming that's irrelevant to my situation here.
Roku does not support volume control in the player, nothing you can do if you want that.
OTOH you keep saying "toggle" - if you meant to toggle mute/unmute, there might be a way, depending on which component is being used.