I don't know your use case, but my experience tells me that people uses react in places where it is absolutely not necessary.

Having state both in the front-end and in the back-end multiplies the complexity of any project, and the gains are only worth if you are (or you have) a good UI designer.

For the rest, the good'ol Rails + Turbolinks, jQuery and SJR can do a fantastic job, without having to think about synchronizing several sources of truth.