It doesn't look like a strict review is being done, there are no guidelines as to what appropriate history should look like, what to tell people who are denied (can they ask again? how long do they wait?), how long someone should be up for review (I've seen a day, an hour, 24 hours, a "few hours" etc.).
I think that's intentional to reduce bureaucracy. The way I understand it, the idea is that a single admin is enough to promote, there is no need to give anyone else a chance to review. If an admin decides, in their judgement (which is considered trustworthy, otherwise they wouldn't have passed RfA), that the person can be trusted with rollback, then they can give it to them. There isn't meant to be a complicated and detailed review process.