you can chose portrait or landscape in the console. this works for both mobile and desktop.
unfortunately on Ipads the game rotates, very irritating. So either you can have a screen saying "turn your device into *** mode" when they hold their ipad in the "wrong" orientation. or you design the game to work both ways...
At least that is how I have found it working.
regarding aspect ratio and resolution the same goes as for a normal mobile game, there are tutorials for it.