The duties of an affiliate manager vary from place to place.
They all are supposed to be answering questions from affiliates regarding the affiliate program.
They may or may not, work on the affiliate site, provide the banners (most order them from graphics), provide links, woo new affiliates, represent the casino to affiliates at conventions and and and...
Some places have large affiliate programs and employ many aff managers, some only have one.
Affiliate managers are paid widely varying wages and/or comissions.
They also have varying levels of decision making authority, from none to free decision power relating to % paid out to affiliates and many other decisions.
They have to state the T&C for affiliates on their websites.
www.affiliateguarddog.com monitors these and reports changes, since these are considered contracts and can't be changed retroactively (just like player T&Cs).
Most affiliate managers work very hard, and then of course there are some dead beats.