Could not find the specified membership provider

I am building a new website using the Visual Studio template. I have a login.aspx page which I hope to point at a roles.xml file created using azman. But it cannot find the membership provider. 
The asp:login control uses MembershipProvider="FormsAuthRoles" which is set up as a rolemanager in web.config
Can a rolemanager act as membership provider?
In security of azman roles.xml file I've added network service and IISUSR account as administrators
 
Here is chunks of relevant code:
<asp:Login ID="LoginUser" runat="server" EnableViewState="false" 
        RenderOuterTable="false" MembershipProvider="FormsAuthRoles" >
        <LayoutTemplate>
            <span class="failureNotification">
                <asp:Literal ID="FailureText" ...