How to use fields from aspnet_tables on a Custom table

Hi, I'm doing a Basic Web Site for a project, and i came across a problem.
Basically, one of the requirements of the Web Site is to have a table that contains the Users that register on the site. Basically it has to have something like User_ID, User_Name, Password and Role....(I created the roles ("Basic User" and "Admin"))
What i had in mind was to create a table that has the ID starting at 1 and every time someone registers, it adds the username,pass and role... i.e.(1 User1 Pass Basic User
              2 User2 Pass Admin   etc..)
The thing is that i cant seem to be able to get those fields from the tables (aspnet_Users, aspnet_Roles) all on one custom table with an id that starts at 1 ... what i want is every time someone registers the id is incremented by one and the user added to the table and to associated with that id ...
I hope i making ...