Looks like you're bit mixing the usage of persistent and non persistent for the process engine and to be honest no idea what you're trying to achieve. If you would like to have non persistent process engine then that would not make sense to set entity manager. You could directly use RuntimeEnvironmentBuilder.getDefaultInMemory. That will provide you most of the elements configured for such usage. If you need persistence for process engine then use RuntimeEnvironmentBuilder.getDefault.
the last environment entry should not be set when entity manager is already given to the RuntimeEnvironment. Could you provide stack trace that was thrown there?
That did the trick, and i'm not getting any exceptions from drools ... i was definitely mis-configuring the environment.