Which one to use in Room: LiveData or RxJava?

Normally working with views it's often good to use LiveData. It automatically manages subscription, works really well with DataBinding library. it's sort of a data holder that is lifecycle aware as oppose to stream of data (Rx Concept).

In other cases I would suggest using RxJava which has powerful operator chains for transformation and concurrency. Hope it sheds some lights on your understanding.