Pixel Dungeon is the roguelike I play the most on my Android. I can't say exactly IF or HOW "deep" it is, but it is very well-polished, it recieves regular updates (by that I don't mean twice a year, but rather once a week), it is free, it is extremely hard.
If by "depth" you mean "many options, and complex customization" then no, it is not deep at all.
Please check it out.
And on the topic, I am considering starting a thread on this roguelike to share experiences - I am only playing mage, and I got quite far ONCE, but most of the time I just die against pretty early monsters while feeling I have been cornered and am forced to just trade blows. If it's something I'm missing, I'd love to hear that.