Code snippet to implement custom membership provider in ASP.NET MVC

I want to implement a custom membership provider in an asp.net MVC app.   I am already using forms authentication and  I have a simple database schema for membership/roles that comprises of two tables as only one user can be in one role.

Here are My table schema is in the code snippet below.

I currently check for a user's role by doing

if (User.userRole.roleName == "admin")////

But want to implement custom membership/roles so I need a code snippet that would implement the provider.   T

USER
UserID           Int
RoleID           Int
Username         varchar(100)
AreaID           int
FirstName        varchar(100)
Surname          varchar(100)
Password         varchar(100)
Email            varchar(100)
CreatedOn        datetime
ModifiedOn       datetime
IsAuthorised     bit


ROLES
RoleID           int
RoleName         varchar(100)

AREA
AreaID           int
AreaName         varchar(100)

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