implement my authorise interface and not use that exist. any help!!

hi everyone,
i need to define a set o f users thats can access my application resource and another how can't , a read some tutorial with simple membership provider but that not exactly what i want , i want that roles be defined from my database, which contains two tables :users , and roles , rely by an one to many relationship ,i look to implement my authorise interface and not use that exist. any help plzzzz