That isn’t supposed to show no roles so that is strange. Could you tell me what exactly you did to create this portal user?
Another alternative is to inactivate the vendor portal user and create a new one with a slightly different username and password like with a space instead of a slash or something along those lines. As long as it’s not the exact same username and password it will let you make a new one. Then you can assign roles.
It’s possible that this was a one of weird glitch. I’m happy to try and get to the bottom of it with you or you can just try to create a new user whatever is easier for you.