Well I pick the roaches because I don't push. What I do is mainly assault forts by myself, so I need my roaches to soak damage. I just place creep near forts and even the core and use nydus to attack and retreat when anyone comes. I have managed to destroy all forts and core by myself using this method. It's also the reason I pick battle momentum and nydus, you barely take damage from forts and cores because I keep a constant stream of roaches, banelings and hydralisks attacking and soaking...