Do I have to order an update to my Roku App for upcoming changes to the Roku App Store and sunsetting of the older layouts?

Only if your App has been submitted prior to 08/2017. The reason is simply that Roku rolled out a few updates to its operating system, including a new content search function for the Roku Channel Store, and new, mandatory hooks to collect more user data. In order to sweeten this mandatory update for publishers, Lightcast.com offers to update the Roku App to a fresh and new design at the same time. Unless your Roku App was submitted to the Roku App Store after 08/2017, your Roku App needs this required update, which has to be completed by December 2018.