Omega is comparatively difficult. It is billed as a game for those who have retrieved the Amulet of Yendor too many times to count. It was the first roguelike with a large countryside and extended plot development. The inventory system is powerful, but the complexity can be off-putting. Omega is strictly text-based.
Omega saves games in /home/rogue/ but they can only be loaded from the command line. To do so, go to the Apps menu, Command Prompt, and run sdlterm. At the command prompt run "VJKAPP=omega omega /home/rogue/savedgame" where savedgame is the file name for the saved game.
You can find more information about omega at http://www.alcyone.com/max/projects/omega/