If you will be needing the value that the rolldice method created, then
you should have it return a value. You could call it from main or from another method. It depends on your needs.
public int rollDice(your parameters if any)
{
compute value
return value
}
You can call ist like this...
int myValue = rollDice(your parameters if any)
There is a very good tutorial at Sun's site too.