If these are truly Roku tv's, and not your use as metaphor for all smart tv's? Then I would suggest a remote like the Insignia 3 in 1 universal remote sold at Best buy:
Insignia™ 3-Device Universal Remote Black NS-RMT3D21 - Best Buy
It's a three-device remote but only has two device buttons TV & STB. The third device is Audio. This remote is great for Roku tv's, it has a code 4398 tailored for Roku tv's. You can re-mode the STB for tv device and program the same code to both devices, pressing either one won't get the owner confused and lost.
Roku tv's use two IR code sets, majority uses the same code set, two brands Hisense & Sharp Roku tv use a different code set. But those two last brands accept both code sets. So really there is only one code for all Roku tv's. Which is 4398 in UEI made remotes like the Insignia. Code 4398 will also give them direct access to channel numbers 0-9, for direct entry of channel numbers.
