I recently bought an Ultra and gave my old Roku to my daughter. When I went to hook the Ultra up, everything went well until I tried to run the HDMI to the sound bar.
The Roku tries to Auto select 1080p and it works for a moment and the.lm everything goes black. I cannot get the Roku and the Panasonic soundbar to play well together.
The TV does not have a dedicated ARC out and if I use an optical cord, I can get sound - but now nothing controls the soundbar … which is a drag - because everything worked with the older Roku.
Have you tried taking the display type out of "Auto detect" from Settings->Display type?
Try getting universal remote that controls a tv, streamer, and soundbar like One-For-All urc-7935 Streamer universal remote. Its one device remote that controls three types of devices, different sections of the remote are for each device. Usually $16.88 at walmart.