Dungeon Plunder Tower of fortune 2 King Cashing 2 RPG Slots Slot RPG Nico's adventure These are the ones that I can remember. Dungeon Plunder, Tower of fortune 2 and King Cashing 1/2 are the best in my opinion.
You might also give Robotek a look. It's not really an RPG, but it does have leveling and upgradable abilities, and has a great slot mechanic.