How can I edit my city without losing my roads?

There is no way, so make sure you got the right layout before upgrading roads.

I play another game that has created an editing station. It allows you to remove everything and re place. It's turned out to be a very cool feature of the game. It has enhanced my enjoyment and I play longer.

Choose the road icon, then choose the bulldozer icon, then select the road you want to remove. Hope this helps.