I know nothing about CEC, but the Voice Remote is kind of two remotes in one. It uses Wi-Fi direct to control the Roku and infrared to control the TV. It's sort of like it has a built-in universal remote that requires configuring it for the TV brand. How CEC fits into the equation I don't know.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.