How to design database for authorization and authentication

If user.IsInRole("Admin") Then
  deleteButton.Visible = True
else
  deleteButton.Visible = False

public interface ICustomRole
{
  bool IsInRole(string userName, object[] params roles);
}

public class MyCustomRole : RoleProvider, ICustomRole
{
  public IsInRole(MembershipUser user, object[] params roles)
  {
    if (roles == null || roles.Length == 0)
      throw new ArgumentException("roles");
    // Put your logic here for accessing the roles
  }
}

bool isValid = ((ICustomRole)Roles.Provider).IsInRole(
  User, new[] { "Admin", "Moderator", "Validator" });

if user.isInRole("Admin") then
  deleteButton.visible = true
else
  deleteButton.visible = false

if user.isInRole("Admin","Moderator") then
  deleteButton.visible = true
else
  deleteButton.visible = false

User(UserID, ...) PK = UserID

Role(RoleID, RoleName, ...) PK = RoleID

UserHasRole(UserHasRoleID, UserID, RoleID) PK=UserHasRoleID ; Unique= (UserID, RoleID)

public class YourSqlRoleProvider : System.Web.Security.RoleProvider
{
    private string ConnectionString { get; set; }

    public override void AddUsersToRoles(string[] userNames, string[] roleNames)
    {
        // logic here
    }

    public override string ApplicationName
    {
        get
        {
            throw new NotSupportedException();
        }
        set
        {
            throw new NotSupportedException();
        }
    }

    public override void CreateRole(string roleName)
    {
        throw new NotSupportedException();
    }

    public override bool DeleteRole(string roleName, bool throwOnPopulatedRole)
    {
        throw new NotSupportedException();
    }

    public override string[] FindUsersInRole(string roleName, string userNameToMatch)
    {
        throw new NotSupportedException();
    }

    public override string[] GetAllRoles()
    {
        // logic here
    }

    public override string[] GetRolesForUser(string userName)
    {
        // logic here
    }

    public override string[] GetUsersInRole(string roleName)
    {
        throw new NotSupportedException();
    }

    public override bool IsUserInRole(string userName, string roleName)
    {
        return GetRolesForUser(userName).Contains(roleName);
    }

    public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config)
    {
        this.ConnectionString = ConfigurationManager.ConnectionStrings[config["connectionStringName"]].ConnectionString;

        base.Initialize(name, config);
    }

    public override void RemoveUsersFromRoles(string[] userNames, string[] roleNames)
    {
        throw new NotSupportedException();
    }

    public override bool RoleExists(string roleName)
    {
        throw new NotSupportedException();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <connectionStrings>
        <clear />
        <add name="YourConnectionString" providerName="System.Data.SqlClient" connectionString="connection string here" />
    </connectionStrings>
    <system.web>
        <roleManager defaultProvider="YourSqlRoleProvider" enabled="true">
            <providers>
                <clear />
                <add name="YourSqlRoleProvider" type="YourSqlRoleProvider" connectionStringName="YourConnectionString" />
            </providers>
        </roleManager>
    </system.web>
</configuration>