Is there any chance we can get remove roles on purchase to go with adding roles on purchase?
Technically, I would say sure, why not, but... Could you describe the case in which you want to do this? It seems to me at first sight this is quite a specific need?
The main reason for this would be if you have a product which handles a membership type. If a user has say a role that gives them permissions as one type of member. When they upgrade by purchasing a product you want to set the new roles for that membership and may want to remove the role for the old membership.