After a bit of searching, I have found that the Bolva 55BL00H7-01 is controllable with a Roku Voice Remote using "Mitsubishi TV code 4".
Power/volume up/volume down/mute all work.
Thanks for reporting your findings.
You are actually amazing.. I don’t know how you figured this out, but it instantly worked seamlessly. They need to change this.
Thank you Thank you Thank you! I was losing my mind with this TV and was almost ready to buy a new one because I hate having to use more than one remote.