Multiple Rules based on the same event not working

I have 4 Rules based on the same event - "After updating existing content".
Content type has 12 fields, and I want to auto-assign roles to the author based on how many fields he entered.
He will be
Rule 1 : Role1 if he entered SetA of fields,
Rule 2 : Role2 if SetA + SetB,
Rule 3 : Role3 if SetA + SetC,
Rule 4 : Role4 if SetA + SetD

Other than assigning roles, I added another send email action with the appropriate content in it. E.g. if Rule1 is triggered, and executed, the email's contents will be Rule1, so that I know which ones got triggered.

When I entered all fields, I received all 4 emails. Thus, the 4 rules are triggered. But the role of the author ends up as Role4 only.

Does the role assignment action actually appends a new role, or erase the previously, and assign the rule's one exclusively?

Thank you if anyone can point me in the right direction, or explain what might be going on.