If I may suggest one helpful and relatively easy/inexpensive thing Roku could do, purely as a software update: without changing bundled remotes, simply add infrared button codes for digits 0 through 9. The NEC infrared protocol Roku uses allows for 256 possible codes, of which no Roku seems to use more than 24. I understand you want to reserve most free code positions for future sponsored buttons, but reserving 10 for digits would still leave about 85% free for this purpose.
This way, the included remotes can still be small and simple-looking, but third-party remote sellers could provide inexpensive aftermarket options for people who want direct number entry. There are already many vendors like this across Amazon & eBay, and some listed remotes do already include digits ... they just won't work with a Roku.
Since digit entry is recognized now for Roku TV local-channel tuning over the networked ECP protocol (thanks!), as with my example script above, and probably some other apps listen for digits too, no application-level changes should be required.
This wouldn't help people with Streaming Sticks, those lacking an IR receiver, but ever other model of Roku and Roku TV could benefit.