If you write JSX. What would be the benefit of using html anymore? Your own components can be the same on web or native. The base components might be a bit different but that isn't difficult to learn.
One of the big pieces in React Native was reimplementing flexbox positioning (they did it using randomly generated test cases in a TDD-based process; described in the "diving deeper" video iirc). So as long as you use flexbox to position your html, it should be pretty portable to react native.
<Carrousel> <Item></Item> <Item></Item> </Carrousel>
On the web you might use a div with overflow:scroll on native a scrollView.