function test()
{
    setInterval("test1()", 2500);
}

function test1()
{
    var ele = document.getElementById("roller");
    var str = ele.src;
    var index = str.indexOf(".gif");

    var currImage = (parseInt(str.charAt(index-1)));
    var totImage = 10;

    if (currImage >= totImage)
        currImage = 1;
    else
        currImage++;

    ele.src = "images/" + currImage + ".gif";
}