public void rollDice(){
check.setIcon(Dice3);
// If the new icon is larger/smaller than the older
// one you might need to ask for a new layout (but
// likely not). You just have to try and see if you
// need it. You do that with the JComponent method
// revalidate or the Container method validate.
check.revalidate(); // Often not needed.
// Generally needed for this.
check.repaint();
}