[2020] Roundabout gets deformated

It happens because the curved segment gets split in two new bits if you connect to anywhere that doesn't already have a node. The trick is to create more nodes in the right place and then connect to them. Then it doesn't deform. You can do that by adding a cross inside it, though you will likely need Fine Road Anarchy 2 to do that for any smaller roundabouts. This video shows how it's done.

https://www.youtube.com/watch?v=peHm79rw6Qs