Will I be rostered for all the hours I put down that I am available?

Not necessarily. If you are asked about your availability, you need to specify a range of times and days which you can work each week. Based on this information you may be rostered within your available time frame once you commence work. However, if your circumstances change, once you commence employment, you can discuss these with your manager and agree in advance upon changes that need to take place with your current roster.