To the best of my knowledge, you can't change the names of default attributes.
You could, however, add some custom attributes to your camera, name them whatever you like, and then connect them to the default transformation attributes. Then when you edit your custom 'roll' attribute, the camera's default 'Rotate Z' attribute will automatically change too.
None of this needs MEL, but if you're looking to practice it, you can certainly use MEL. Look up the commands 'addAttr' and 'connectAttr' for starters.