Ummm...you are declaring this function to take *THREE* PAIRS of image names and image file names:
function roll(img_name1, img_src1, img_name2, img_src2,img_name3, img_src3)
document[img_name1].src = img_src1;
document[img_name2].src = img_src2;
document[img_name3].src = img_src3;
But then when you *call* that function you only pass *TWO* pairs:
So why are you surprised that nothing happens in the third image???
Try again, this time passing THREE pairs.
But I don't understand why you WANT to change 3 images. Your first paragraph only talks about changing two images.