This is a watchface version of Rosewright Chronograph. Please install Rosewright Chronograph (listed among the apps) if you are looking for a functional chonograph watch.
Rosewright C is a watchface you can run for everyday use on your Pebble with the look of a fancy three-dial chronograph, but as it is a watchface and not an app, the start/stop buttons aren't functional and the chrono function is disabled. However, it supports the normal Pebble functionality for a watchface (timeline view, health view, and so on).
If you install both Rosewright C and Rosewright Chronograph, you can assign Chronograph to a quick-launch button to effectively enable the chronograph functionality at a touch of the button.