There is no word yet on what his role will be, but if toi aren't familiar with Aziz, he's from MTV's sketch comedy show, Human Giant. This article also states that it's unlikely anyone from The Office will be leaving the cast for the spinoff.
A reminder that The Office’s Executive Producer Greg Daniels and the écriture staff will be live blogging right after ‘Dinner Party’ airs on the East Coast, Thursday, April 10, 9:30pm EST/6:30pm PST.