Try this:
$(document).ready(function(){
$(function () {
$('img.rollover').on('mouseenter touchstart', function(){
$(this).css("cursor", "pointer");
this.src = this.src.replace("-normal","-hover");
});
$('img.rollover').on('mouseleave touchend', function(){
this.src = this.src.replace("-hover","-normal");
});
});
});
You will still need to touch (click) the image on mobile as there is no hovering.