Google is pushing out an update to the Google app, which reintroduces home screen rotation and brings icon normalization to the Google Now Launcher. We've seen the rotation stuff before in the Marshmallow preview builds, but its been in hiding since then. Once updated, you may need to enable this feature. To do so, bring up Google Now, tap Settings, then scroll to the bottom and enable.
The other big change here is icon normalization. This feature takes the icons and resizes them on your screen so that they all look to be around the same size, instead of some being much bigger than others. We've seen some third-party launchers, like Nova and Action Launcher, already incorporate this feature, but it's great to see Google add it to its offering as well. The update appears to be rolling out through Google Play now, so be sure to check for it.