Heart of the Swarm- Evolution Guide: Devouring and Inextinguishable

Hydriotic Bile: Roaches deal 100% more damage to Light targets.

Among the Zerg, roaches stand out as being the only inexpensive unit with the Armored keyword.  While this isn’t odd for Terrans, who have Firebats and Marauders, it’s unusual for the Zerg and basically unheard of for Protoss.  The added damage to Light targets can mean a huge swing in battles with Protoss and Zerg small units, and still proves useful if a Terran enemy force is leaning on vultures and/or marauders in addition to marines.  This becomes particularly meaningful once you have either corpsers or vile roaches- corpsers will cascade even faster through Light enemy units, and vile roaches will cut through the units you’re less interested in slowing down faster.  Both these effects are useful- but only if you’re facing notable worries with numerous light enemy units.

Adaptive Plating: When below 50% Life, your roaches gain +3 armor.

While it doesn’t sound like much, +3 armor can make a huge difference.  Particularly given the high trigger threshhold, this will go a long way towards saving your roaches while they’re still shooting.  If you find using the burrow function in combat to give your roaches a chance to heal is too micromanagey for you, this can be very useful.  It also gives a strong boost to vile roaches, who want to keep shooting so they can keep their targets slowed and ineffective- burrowing just isn’t as nice if returning to the surface means immediately losing big chunks of the Life you just healed to an enemy who is no longer slowed.  Corpsers won’t need this as much, since they’re supposed to be spawning roachlings at a steady rate, but it can come in handy now and then against heavier units.

Tunneling Claws: Your roaches can move while burrowed and their burrowed healing rate is doubled.

This is a fantastic adaptation, and one that is usually considered standard in play outside of campaign mode for its overall utility.  The accelerated healing means that burrowing your roaches to patch them up keeps them out of combat for a shorter time, and the ability to move while burrowed means that they can often pop up in unexpected places and commit deadly ambushes.  The healing rate is a special highlight for vile roaches, who may find that they now heal before their slow effect wears off of their targets.  This is less useful to corpsers, who would prefer to advance behind a slowly accumulating wall of roachlings, so consider carefully before trying to use this with corpsers.  Either way, though, it’s an excellent option for keeping your roaches of any kind functional in all situations.  It’s just a pity the computer players in the campaign always have near-perfectly placed detectors to keep you from really pulling off the nastiest ambushes.