I've checked the source and the problem is that the root element (.vis-timeline) is always hidden as soon as you add option for rollingMode. If you open DevTools and set element to visible it works normally.
After looking for possibilites, I've tried the previous version (4.20.1) with the same code and it works.
The demo for rolling mode functionality is not working: http://visjs.org/examples/timeline/interaction/rollingMode.html
I've checked the source and the problem is that the root element (.vis-timeline) is always hidden as soon as you add option for rollingMode. If you open DevTools and set element to visible it works normally.
After looking for possibilites, I've tried the previous version (4.20.1) with the same code and it works.