Update: Yes all old Roku boxes had a way to reset them but you needed a paper clip to reset it. Now there is a real physical button you can press with just your finger.
New FCC documents show a reset button on the bottom of what is thought to be a Roku 4 with the model number 4400X.
All new boxes must show how the FCC marking will appear on the device. On Roku’s it is located on the bottom of each box. Here you can clearly see the FCC markings and a reset button.
So it looks like the rumors of a reset button are correct and the reset button will be located on the bottom of the Roku.