Chaffetz and Gohmert may be working behind the scene with planning and organizing the evidence. They may also be brought in to question specific witnesses.
They may asked to function as chief of staff and legal advisors to the Republican side. Those roles may be as important as those of the GOP members, aside from Gowdy.
What is actually most important is the staff that will be assembled to support the committee. We most likely will never know their names.