It is sufficient only to know this much, in order to demonstrate the impartiality and righteousness of God, that, conformably with the declaration of the Apostle Paul, there is no acceptance of persons with Him, who rather disposes everything according to the deserts and moral progress of each individual. So, then, the angelic office does not exist except as a consequence of their desert; nor do powers exercise power except in virtue of their moral progress; nor do those which are called seats, i.e., the powers of judging and ruling, administer their powers unless by merit; nor do dominions rule undeservedly, for that great and distinguished order of rational creatures among celestial existences is arranged in a glorious variety of offices. (Book I, Chapter 8, Part 4)

Is there a role for merit in grace? Is there a role for grace in merit?

Perhaps in this way: I cannot imagine any sort of angel who has not successfully submitted every hope and desire to loving God.

Such submission is surely a form of moral progress and it allows the Holy Spirit to inform and empower.

The image is Good and Evil Angels Struggling for Possession of a Child by William Blake