The first Roku TV platform was launched in Fall 2014 with TVs by TCL and Hisense; those TVs are still getting software updates -- 9.1 was released earlier this year, and Roku OS 9.2 is in the process of being pushed to all models now. Releases often occur in stages, with Roku monitoring a release to see if there are blocking issues that need to be fixed before doing a wider push. Also, Roku OS releases do usually arrive for set-top boxes before they arrive on TVs due to the complexity of the TV feature sets and validation on all the models.

You can see a hardware comparison chart at https://developer.roku.com/docs/specs/hardware.md -- Liberty was the platform name of that first generation of Roku TVs.