How to use common master page for different roles?

I want to use common master-page for different roles, i just want to set different themes and menu items according to roles, could somebody guide me on how can i use in my membership code in the same master page ?

For my current code i downloaded the membership code from the codeplex that set different master pages for different roles, but i see when i have to make some page common for all roles that is to be access according to roles, i have to make the page page in each roles folder and have to set it to master page menu according to role, so i want to use a common master page for all....

Solution

You can change the master page programmatically during the OnPreInit method:

protected override void OnPreInit(EventArgs e)
{
    base.OnPreInit(e);    

    if (Roles.IsUserInRole("Admins"))
    {         
        Page.MasterPageFile = "AdminDefault.master";
        return;
    }

    Page.MasterPageFile = "Default.master";
}

If this functionality will be used by several or more pages, I would consider putting it in a base class that the pages can inherit from.