Due to the repetitiveness of Risk battles, players sometimes come across the issue of whether or not a valid dice roll has been made during a battle to conquer a territory. There happens on occasion to be a defender who, expecting yet another attack, carelessly rolls the defending dice before the attacker rolls and decides that he will continue the assault. The attacker would be at an advantage if he were able to view the dice roll he is up against, especially when the defender rolls a six (meaning certain defeat for one of the attacking armies).
One option is to allow the attacker to have the option of deciding whether to halt his attack or confidently roll against a relatively low roll by the defender. This has the effect of penalizing the defender for his carelessness.
A second option is the attacker may still decide whether he wants to continue, but he will be forced to forfeit an army if the defender has rolled a single six or forfeit two armies if the defender had rolled double sixes. It is important to note that this option potentially allows the defender to manipulate the situation a bit, especially in cases where the subsequent battles require a precise number of armies being brought through the battle at hand.
A houserule that helps defending player is that after the attacker rolls his attacking dice, the defending player rolls first one die, and then he decides if he throws the second die depending of the dice already thrown, he can choose to lose just one army or make the attacking player lose one army, or risk throwing the second die, the battles will have different outcomes depending of the dice, it gives defending player the sense of deciding, and not just throwing dice to see who rolls higher, this makes battles more interesting and even if the attacking army outnumbers the defending player's army, using strategy can slow attackers down.
Example:
Yellow Army attacks with 7 armies from Argentina to Brazil who has 2 armies
Red Dice: 5,3 and 1
Defending player rolls first die 4
The defending player can choose to lose 1 army... or thow the second die resulting with a 5 that beats 5 and his 4 beating 3
Or instead of rolling a 5, instead it is a 2, making defending player lose 2 armies, instead of one that she could of lost 1 if not thowing the second die
This has multiple outcomes depending of the decisions made during battle.