Primal roaches are primal zerg creatures based off the Zerg Swarm's roach strain. They are one of the many strains whose essences, according to Abathur, were stolen by the primals shortly after the Swarm landed on Zerus.
Primal roaches are similar in basic appearance to normal roaches, though they have different colors, have a slightly more bulbous carapace, and possess larger claws. They also have more health than normal roaches in the campaign.
Kerrigan, in her Primal Queen of Blades form, can summon sacs containing a group of primal zerg consisting of primal zerglings, primal hydralisks, and primal roaches. These units have a timed life and do not have any of the benefits normal roaches gain from the evolution pit.
The rate of healing increases with the Tunneling Claws upgrade to a rate of 10 hit points per second.
Many zerg ground units may burrow, become invisible and may be revealed primarily by detectors, and may not move or attack. Exceptions are the roach, which may move while burrowed, the infestor, which may move and cast Infested Terran, and the baneling, which can detonate while burrowed.
Some units can unburrow via autocast, causing them to emerge and attack when an enemy moves into range.
The ability is not smartcast.