That's because the size of the images isn't exclusively set by the carousel. Rather, it's set by Wordpress settings (Dashboard > Settings > Reading) and of course, your graphics editor, to resize the images to the same, standard height so that Wordpress doesn't have to attempt scaling.
Then, within a carousel, you may find styling (CSS) that controls how images appear within the slider. If the carousel has such styling, it can be adjusted (I use Firebug for Firefox or Chrome's Inspection Tools) after finding it, testing it, copying the working code and pasting it into Dashboard > PageLines > Site Options > Custom Code.
If your CSS has even dimensions for height and width, you may want to remove or modify the width to something like min-width: 100px; so that it allows your images to be of varying width, but set the height to a static dimension, so all are the same height as the images you've used.
Really, not difficult.