Hi Maya, most species of insect increase activity as we move from winter into spring. If the cockroaches you are seeing are the large, shiny, black ones with the white stripe around the edge these native ones shouldn't be anything to be too concerned about. There are a handful of species which are introduced which are less desirable as they can come in from drains and pipes and bring germs. Probably the most common of these species in Melbourne would be the German Cockroach, Blatella germanica
. Search online for this species by image and if that is what you are getting there are a number of websites which will offer general advice on minimising cockroach numbers. Or if you can catch one take some images and send them to email@example.com
and we'll confirm for you.