I don't care about the price as long as its awesome and will give me few days of entertainment, I love RPGs, games with good story's, please no puzzle games also make sure I can pay offline to since I won't have online, and remember anything but puzzle games.
Defender Chronicles II: Heroes of Athelia. You'll get your RPG fix, a ton of strategy, a ton of content, decent story, and endless gameplay. You really can't go wrong with this gem.
Any Kairosoft game is good for a long road trip, because they're addicting, take a while to finish and best of all, are really battery friendly. Dungeon Village has some RPG twists in it or so I've heard.
Here's some personal favorites that'll last a long time and fit your likes. Also do you care about battery life? Lego Harry Potter 1-4 (then 5-7 also after that) Tactical Warrior (also the dev of that game has a new one, Lost Star Tactics out and on sale) Galaxy on Fire 2- don't own it personally (yet) but I've heard those games are really good and its on sale for a buck as well. Gamebook Adventures series
Get Galaxy on Fire 2, it'll certainly keep you busy for a while, and only a buck. great game, i recommend it.
I definitely recommend Galaxy on Fire 2 and Mage Gauntlet. GoF2 is a scifi semi-RPG; pretty fun if you're into scifi stuff like Star Wars. Mage Gauntlet is just an amazing RPG that really shouldn't be missed. Well worth your money especially since you said you love RPGs.
Don't forget grand theft auto 3, aralon, shadowgun, dungeon hunter 2, dead space, and land air sea warfare. All are excellent games.
You can't go wrong with grand Chinatown wars, $10, but extremely worth it for the hours of fun, and if you are creative then try minecraft.
"I wonder what game Ninja will suggest..." Aww y'all know me way too well. You need Dungeon Raid. It's got an endless amount of content. It's a RPG/Bejeweled hybrid.