Pokemon R.O.W.E. v1.9.0.1 is a more significant update to the R.O.W.E. ROM hack compared to the previous minor updates. The jump in version numbers hints at more substantial changes in gameplay, content, or even the overall game structure.  The creators may have introduced new features, storylines, or even a complete overhaul of elements from previous versions.  However, due to the nature of fan-made projects, development details are usually not formally documented.

Pokemon R.O.W.E. v1.9.0.1

Pokemon R.O.W.E. v1.7.4