How many Australian Open courts have roofs?

Question

Two. Rod Laver Arena and Hisense Arena both have retractable roofs, which can cover the courts in the event of rain or extreme heat conditions – both of which are prone to occur during the two weeks of the Australian Open. It was announced early in the 2010 tournament that a funding injection that will see Melbourne Park redeveloped and ensure the Australian Open remains at the site until at least 2036 is to include the construction of a retractable roof over Margaret Court Arena as well.