The 4 tile grid was, originally, sent out randomly as a test, and then removed without warning. Word from Roku staffers was that it would return at some point permanently, either as part of Software version 13.00, or as an independent tweak, unrelated to the version of build number. That time has apparently arrived as more and more of us are seeing it on at least some of our devices. We have also found that it is an independent tweak and not dependent on the Software version or the build number.
When present, the option is found under "Settings" -> "Home screen" -> "Tile size."
The options are "Larger" or "Smaller," with the choice of smaller giving you 4 tiles across.
Various updates are sent out rather randomly it appears. My devices do not typically receive the same updates, including software version or build number at the same time. Your device is supposed to check for updates every time you "turn it on" but you can also force it to check at any time. I often find that this manual update will find and install one or more updates of some kind -- even when performed shortly after tuning on my device and its own check having just been completed. It is only during a manual check that you will get to see what, if anything, is being updated.
To perform a manual update check, go to "Settings" -> "System" -> "Software Update" -> "Check now"
Note that you will see the date and time of the last check, as well as the date and time of the last "update" although the latter apparently refers to an actual "software" update, but not other updates. Many things can be updated besides the version and build, such as updating various apps (channels) and some minor items they do not name, but when being installed you will see them listed in cutesy terms like "fine tuning the warp drive" or "enhancing shields." These unnamed enhancements seem to be what add the various menu options that pop in from time to time, and also adds the "Tile size" option that so many of us are looking for.
I hope that helps add some understanding, though it may not do much for enhancing your patience as you wait for the "Tile size" option to arrive on your device.
