Right now if you have a web role hosted on azure and you want your .aspx page to be displayed when user hits to root url of *.cloudapp.net then you don’t have any choice to do it from Windows Azure Management Portal.
However this setting can be configured from web config file before deployment to Azure. Under <configuration> section add following snippet tag –
That’s it! You are done. Now when user hits to root url of cloud application, he /she will be redirected to page you have set up.
Hope this helps.