Extension: Role Based Registration Form
Description
Role based registration form tool allows you to bound user roles to registration forms. Assign the bound role automatically for the users registering through the form. Alternatively, allow users to choose a role themselves from a list of pre-approved role selection. The option adds a new drop down field inside the form.
WordPress Registration Plugin
RegistrationMagic Silver
Notes
This extension is part of RegistrationMagic Silver. Note that RegistrationMagic extensions are part of bundles; extensions are not available (or sold) individually.
Link
Role based registration form extension is available here.