Melbourne has many rooftop bars, but only a few are accessible of course.
Firstly, here is a site that has info on bars:
melbournebars.com.au
Unfortunately, on this site you have to look at “features” under each bar entry for “disability access”.
Zomato.com/melbourne
The search on this site has all sorts of options, such as “wheelchair access”, “location”, reviews and so on.
concreteplayground
This is a new site (2017). If you hover over the little building symbol on the top right and select an option you get a whole lot of filters on the left. Right near the bottom you can select wheelchair access.
Here are some that I know of:
Nineteen-Forty
This is a new one (2017) on the roof of the lovely Rivoli Cinema.
The Corner Hotel rooftop bar
I have seen some great acts in this pub in Richmond. They have a dodgy makeshift ramp they put out for wheelies although there have just undergone a renovation so they might have made it a bit easier. I know they put a lift in so wheelies can get to the new rooftop bar.