No, it can't control the roku streambar directly. Firestick controls tv & av receivers/soundbars, the volume commands from the roku streambar remote is neither tv nor audio device. Its streamer volume that not only the roku soundbar & streambar accept but ALL roku models accept these commands. These are roku commands when a roku sees them initiates a hdmi-cec signal sent over the hdmi cable to control whatever tv brand its connected to, thats way you don't have to program a tv brand in, it controls all brands that have hdmi-cec feature and its turned on.
The Firestick remote won't control the streambar directly, but it will control your tv's volume which in turn controls the streambar, by hdmi-cec. streambar controls the tv and tv controls the streambar by hdmi-cec.
Edmund
