Active Directory Memebership Provider with Asp Net SQL Role Provider

Is this possible???
I have my asp.net 4.0 website successfully configured for Active Directory Memebership Provider and I'm logging in without issue. I would like to create some custom roles for myself and other users, outside of active directory using the Asp Net SQL Role Provider. Can these be mixed in the same website? When I bring up the WSAT and click the security link, I get the following error message: "The Active Directory membership provider has not been configured to support search methods".
What attributes of the AD membership provider does this refer to?
Do I have to convert this website to a web application?
Here is my web.config for reference. You can see that I have configure the membership node for AD use and the roleManager node for sql:
<configuration> <connectionStrings> <add name="ADService" conne ...