Benjamin acts as an advisor to Don King; possibly like a consigliere.
The same figure appears again in Book 2, text update 34 reciting (or perhaps only thinking) a piece of Rhyme-o-Mancy in which he criticizes Don King for spending schmuckers on Jillian and Faq. In real life, Ben Franklin was a brilliant polymath. It may be that Benjamin is similar to Wanda in being proficient in many magical disciplines outside his own, but unlike Wanda, and more like Sizemore in actually finding them fascinating. Since he is 'cancelling the antsy' with his rant, it may be that Benjamin is the only thing preventing Caesar Borgata and the warlords from carrying out a coup.
Real World References
Benjamin's name might come from the slang use of "Benjamin" to reference large sums of money, due to the appearance of Benjamin Franklin on the U.S. hundred-dollar bill. (On-Line Slang Dictonary)