Yes, he is taking an RB spot. I know that is not his primary position for this team, but it is a spot that he takes on the active roster.
I respect McDermott's emphasis for having a strong Special Teams unit, yet I don't think that re-signing Jones is necessary.
Let's stick with the players we currently have on the roster. Tyler Matakevich, Daryl Johnson, Siran Neal & Jaquon Johnson are all very good special teams players, let's stick with what we have, and use our money for a different position.