So as a disclaimer im a total noob with dnd 5e is the first edition ive ever played. so with that in mind here is the review. Rouge Ninja is ok. the sneak and other rouge qualities are great. Balanced as far as i can tell. so my only complaint in detail is that the ninja should have something simular to the warlock.

The Warlock has pacts and patrons. so im thinking the ninja should have schools and particular chosen styles limited to the element chosen. in order to have 2 style one would have to multiclass.

im certain you see my idea at this point. but the rouge ninja as is seems to be fine as well