What ways are there for a Standard Werewolf deck to handle Ratchet Bomb?
On color

Green:


The obvious choice in your situation is Full Moon's Rise.  It buffs all your werewolves while it's in play and you can sacrifice it to save all of them from a Ratchet Bomb.  
Another direction is Withstand Death, but this only provides the means to save creatures on an individual basis and is a sideboard card at best.  
Asceticism gives you the option of regenerating creatures and hexproof on top of that.  However, regenerating a large number of werewolves could get expensive. 


Artifacts:


Phyrexian Revoker is another great way to ruin Ratchet Bomb's day, but it has its own limitations and weaknesses as a creature.
Sundial of the Infinite would work as long as they are trying activating the Ratchet Bomb on your turn.


Off color

For others who might have the same concerns in a different mana base.

Blue:  Obviously any counter is going to prevent Ratchet Bomb from ever entering the battlefield. 


Steel Sabotage would be a good one specifically for countering Ratchet Bomb.


Black:


Memoricide can remove any Ratchet Bombs that are not in play thus preventing them from ever being used.  
Surgical Extraction could be used for a similar effect, but unfortunately can only be used if a Ratchet Bomb is already in the Graveyard.


White: 


Stony Silence can prevent the activation of a Ratchet Bomb.  
Nevermore can be used to ensure that Ratchet Bomb is never cast.