There is no word yet on what his role will be, but if u aren't familiar with Aziz, he's from MTV's sketch comedy show, Human Giant. This artikel 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 writing staff will be live blogging right after ‘Dinner Party’ airs on the East Coast, Thursday, April 10, 9:30pm EST/6:30pm PST.