$(document).ready(function()
{
    $(".roll img").hover(
        function(){this.src = this.src.replace("_off","_on");},
        function(){this.src = this.src.replace("_on","_off");}
    );
	
	$(".roll1 img").hover(
        function(){this.src = this.src.replace("-1","-O");},
        function(){this.src = this.src.replace("-O","-1");}
    );
});