The Common Shining Cockroach is native to Australia. It is a glossy black or dark brown cockroach with pale margin around the front half of the body. During the last decade or so, numbers have increased in cities such as Sydney and Melbourne where they often wander into houses, but they are not a pest species and not a health risk like some of the introduced cockroach species. If you find one in the house, try to put it back outside rather than kill it, as they are beneficial to the garden by breaking up leaf litter.
Common shining cockroach

A species found in Melbourne.