Have a look at some of the Final Fantasy games. Not the spin-offs; the real deal, Roman numeral Final Fantasy games, especially VI through IX. The earlier ones, while neat, are a little too dated. The downside is that they are as expensive as they would be if you were buying a clean copy for a console...up to $20.99 for IX. Still, that gets you a hell of a lot of high-quality RPG gameplay. Earlier games are cheaper, but they are also more basic. Also, another issue with these games is that they were not originally designed for touchscreens. I much prefer playing any of them on a console or PC emulator, but for playing on the go they are ok.
For something that is a lot cheaper ($1.99) and perhaps even more fun, you might want to look at The Bard's Tale. In fact, it might even be a better choice regardless of price. It's a port of a game that's been on many platforms and is much loved by many players. I still have a physical copy for the OG Xbox - it was good then, it's good now.
There are also quite a few KEMCO published JRPGs on Google Play, but I haven't played through any of them, even though I do have one on my tablet. Might be worth checking out, but I can't personally say how good they are. A lot of people seem to like them, though. Just go to the Play store and search for KEMCO and they will come up.