I would recommend you to do this achievement after the end of the game cause i dont have sure in what part of the history you get Roland's number, or just check it trough the game if you already have his number.
Roland is a bleached hair guy, he kinda looks bald but hes not, his missions will always have the name "Collection:" in beginning.
Basically you just need to keep calling him for he send missions to you, he will give you some short missions and you will need to do them, pretty easy btw.