There is not a pre-built web editor like there is the WinForms.  However, yes, you could create your own as you can directly access the SF Security BOs.  Using the framework you can create your users, etc.  So if this is a big need, then it is definitely something you can write and implement.

Do you have a WEB version of the Role Base Security Editor or is it possible to create one easily using built in SF commands?

Thanks,

Jeff