Generate a random number within a range but exclude some - http://stackoverflow.com/questions/5520835/how-can-i-generate-a-random-number-within-a-range-but-exclude-some
Set an array with all the values (this is only a valid option if you're only doing small numbers, like the 25 in your example), like this:
var array = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24];
then, pick a random number between 0 and the array length:
var num = Math.floor(Math.random() * array.length);
remove that index number from the array:
var roll = array.splice(num, 1);
Javascript splice() removes indexed items from an array and returns the item(s) as an array. Perfect for your use.
Grab the first index from the roll, since we only cut 1 out anyway:
var yourNumber = roll[ 0 ];
Keep doing for as many rolls as you want. Also, you might want to store the original array as a copy so that you can "reset" the numbers easily.