The remote only carries IR codes for TVs. They cannot be programmed for sound bars or AV receivers. If you have CEC control capability with your TV and sound bar, your Roku remote might control the volume via that method. But it will not control your sound bar via IR.
Let me add that you will never be able to control all three devices completely with a single remote. There are many TV or sound bar functions that their dedicated remotes can control that the Roku remote cannot duplicate. And since a Roku Stick will not accept IR codes, you can't use a universal IR remote for all three.
And just to be certain, your Roku Stick connects directly to the TV's HDMI port without using a cable, correct? If you are using an HDMI cable then it's not a Roku Stick. I had to add that because someone referred to their Roku Express as a "stick", which it is not.
