Roku Remote Can't Connect to LG Soundbar

I have my Amazon Firestick connected to both my TV (for power) and LG soundbar (for sound). It did this automatically. 

However I just replaced my Firestick with my new Roku 4k streaming stick. I was able to get the remote to power my tv on and off, however I can not get it to control my soundbar for volume at all. Can someone please point me to instructions on how to do this?