Thanks for your question! The Treasurer’s main responsibility is to deliver the Budget each year—the Australian Government’s annual statement of how it plans to collect and spend money.
The Treasurer's role has historically involved areas such as Public Service pay and conditions, bank notes, the taxation system, pensions and other welfare payments, postage stamps and the collection of statistics. It also lists many current issues, such as economic and social policy, climate change and international agreements. The Treasury also has a role in supporting business and money markets, as well as providing Australian Government payments to state and territory governments.
By comparison, the Minister for Finance's Departmental website lists responsibility for issues including Budget and financial reporting, managing the Public Service and services enabling businesses to operate.
This is a very general overview only. The roles have areas of similarity as well as difference. You would need to take a close look at the websites of both ministers and their departments if you require more detail.