The problem you describe is the simple case. Because there are no rules or other factors that apply across rolls, you can simply divide the possible winning rolls by the total possible rolls.
Because the order doesn't matter there are 4! (24) possible combinations that win, out of a 100^4 (100000000) possible combinations. That is a rather slim 0.000024% chance of success, or 1 in 4166667.
Jay