How to make a rule select all users of a role?
It appears to me that there is a straight forward solution to have your rule process all those users of a certain role (as in your question): you could an approach to process the results of a VBO enabled view via Rules, whereas your rule performs 2 Rules Actions:


load the VBO list of users that you want to be processed (= those users of a certain role).
add a loop to perform a Rules Action, probably similar to the rule you already have in place, for each user contained in your Views results.


For more details, have a look at the tutorial "How to process the results of a VBO enabled view via Rules?".