I'm not a Room Kit expert but I've found some resources which may assist:
Cisco Webex Room Kit - main page includes all configuration guides, downloads and data sheets plus getting-started guides, administrator guides and api reference guides.
Customization Guide for Cisco Webex devices running RoomOS 10.11 - this is the latest one out and it's listed in the main page linked above. It goes through adding extensions, widgets and Web Apps (a Web App is simply a button on the home page) as well as switches, sliders and buttons, among other things.