This tool is pretty much superceded by the addition of the custom role builder in the azure portal. As such, I will not be improving this tool.
A Powershell program with a XAML interface to create custom roles
Simply download the ps1 and xaml files, enter the filepath for the xaml in the $xamlfile variable and run the ps1.
There aren't any checks for existing roles and there isn't much error handling yet, but these are on the road map.