Help with form authentication against a sql tables.

Hi there people, im developing a site in vwd 2005 using vb.net and  i need to authenticate the users, using my own users table in sql server 05 with form authentication, i 've seen the built in asp.net authentication system but theres a lot of limitations when it comes to adding extra data and stuff, so what i need is to implement my own tables in sql server to authenticate the users against my users table and to create my own roles table in sql server and manage the users roles there too, 
please, examples, to an unexperienced begginer with asp.net?
thanks 
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