Recreate the default user roles without changing/deleting my custom user roles?

I started making my first real wordpress site recently and in my enthusiasm deleted all the default user roles, because I wanted to create my own.

Everything was going honky dory until I migrated my site.
A plugin didn’t really migrate well… and to reset it it uses a script that needs to perform actions to the default user roles.

Now… in order for that script not to fall into error, I need back the default user roles. I have been checking the forum on topics regarding this, but there is nothing that deals with the fact that I want to keep the current custom user roles I created.

So how do I recreate the default user roles without changing/deleting my custom user roles?