in 90's, I played lot of SNES RPG in japanese, without trying to read !
yeah, of course, you miss most of the details, but some RPG have enough visual to understand the story and what to do next.
but in 90's, without internet, translation team, and very rarely released RPG outside of japan, we did what we could.
if you have notion of kana, it's even better as you will understand menus, items, and some of the story
that was my case, few words and few kanji known, enough to play "japanese friendly RPGs", really. sometime you know a kanji visual without necessarily knowing how to read it, but you know its meaning. Maybe not Ninokuni, that would be bad to miss its story. but there are lot of games you can play and understand without really reading or understanding all the sentence. even if it can seem dumb for rpg...
if you want games to learn at the same time, there are zelda games on DS (click on kanji to read its furigana). there are games written only in kana too (but I know only on PS1).