The Roaches are available by Roach Waren building.These units are amazing, they have bonuses against melee units like Zealots , Zerglings and  their unique property is their dynamic burrow ability which means they can move while they are under the ground with extra regeneration (heal regeneration)! They can not attack air units so fast aereal pushes can be dangerous for Roach tactic but this disadvantage can be easily eliminated by spawning new Zerg Queens. We suggest you certainly try this unit against a Protoss or a Zerg enemy. Enjoy!