The sf_user_link table and membership_info

Hi.  

I have been tasked with adding users to roles via a stored procedure.  I noticed the membership_info column in the sf_user_link table.  However, I cannot find a membership table anywhere to retrieve that data from, and there is not a relationship attached to the table.  Is this something I should be pulling from another location, making up, or is there another way I should be handling it?

Thanks!