When you say "root view" is this the root view of the modal path - or the root view for the app as a whole? I'm assuming root of the modal path.
For the button naming problem. You could use "dismiss" as I believe this is used in a couple of native apps - can't remember which at the moment. However, if you use the cancel button you get the benefit of it being automatically localized without you having to do anything. Further, you are not canceling an action in progress - you are canceling an action that the modal view would perform before being dismissed. Check the HIG - around page 157.
If the modal view you are presenting is a secondary flow within your app - done might be more appropriate (thinking the Remote app from Apple when you bring up the control view). And, again, you get the added benefit of automatic localization.
As to left or right: except for some minor exceptions - the expectation from the HIG and native apps is: if it will return a user to the previously viewed screen (either modally or popping off the navigation controller stack), put that button on the left; if it will perform an action prior to returning the user to the previously viewed screen (or dismissing a modal view), put it on the right ("save" in the 3rdView).
The edit button is one of those exceptions, because it has a dual state. The action of entering edit mode, and the done state to leave edit mode (returning the user to the "original" view) - and generally placed on the right.
Some vendors have broken away from this rule of thumb to accommodate lefties versus righties. While some, even at Apple, think this is okay/good - I personally think it leads to inconsistency between apps - which is something Apple recommends avoiding whenever possible. As one of the things that makes applications on the Apple platforms easy to use is a certain overarching UX consistency.