RoleExists - cannot resolve the symbol

Hi, 
I am trying to implement role-based authentication in asp.net application. I have created a database, and set the web.config file to use the connection string. 
Unfortunately, I get "cannot resolve the symbol" error at
if (!Roles.RoleExists(newRoleName)) // Create the role Roles.CreateRole(newRoleName); RoleName.Text = string.Empty;
Any suggestions?

Thanks
...