As far as I know starting alias path is assigned to a User not to a Role. You can have only one starting alias path per user. So that being said - NO.
You can create separate role for each sub site and play with permissions. Which is way more complex
and even more prone to a human mistake then "assigning starting alias path".
I'd say probably in order to avoid permissions setting complexity - i'd say create a report in reporting applications that list what alias paths your editors have access to. This way it is easy to check if something is out of order.