$(document).ready(function (){
	$("img.roll").mouseover(function (){
		var newImage = $(this).attr('src').replace(/^(.*?)(\.(?:gif|jpg|png))$/, "$1-over$2");
		$(this).attr('src', newImage);
	});
	$("img.roll").mouseout(function (){
		var newImage = $(this).attr('src').replace('-over', '');
		$(this).attr('src', newImage);
	});
});