You'd need to disable the Automatic Registration feature of JFBConnect to do this.
Then, depending on how other things are configured, the user will be able to select their profile type:
1) If the "Registration Component" is set to "JomSocial", they can choose their profile type and register using the JomSocial process. Any information that can be pulled from a social network will be pre-populated for them.
2) If the "Registration Component" is set to "JFBConnect, they will go through a mini-registration process where you can select whether they can choose their username, email, password or show other JomSocial fields. They will be able to select their profile type on that page.
I hope that helps explain. If you run into further issues though, just let us know.
Also, please post from the account you subscribed to JFBConnect from.
Thanks,
Alex