The Roundabout properties (3D corridor category) has the checkbox "update corridor" which is enabled in my case.
The issue is if we move/edit the roundabout object in the drawing by grips, we have to open every time the Roundabout properties dialog box and press the [Apply] button to update the corridor.
It would be interesting this option also in the context menu when we select the Roundabout object. The option "update corridor".