If you want to play a roguelike on a portable, you'll need to play something built for portable. I have no specific recommendations... unfortunately, I can't help but compare things to Angband (my drug of choice) and everything ends up too simple by comparison. That's just my problem, though. Android certainly has a lot of roguelike things on it, the Web is full of reviews and recommendations: https://www.google.com/search?q=best+android+roguelike
Take a subnotebook on the train!