Roundabout modeling in ConceptStation


I am designing an intersection using ConceptStation for a conceptual study project. I am trying to model both roundabout and stop-controlled intersection options for comparison. I haven't been able to successful create a roundabout. I tried creating a 1-lane template with a truck apron, and create a circular horizontal alignment, but the alignment will not allow the road to curve enough to create a circle. I am a relatively new user, so I am not familiar with all of its capabilities. 

Has anyone else tried modeling roundabouts in ConceptStation?