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