http://techdocs.shimano.com/media/te...9830609118.pdf

Found this PDF showing Shimano's spare parts list for their 105 rear derailleur. It shows an exploded veiw of the pulleys. This 105 has plain bushings, the most common kind of bearing in pulleys (and simple to work on), but Dura-Ace and some others have sealed bearings.

I found this PDF at shimano.com, under Tech Docs, then the group (105), then the link starting with "EV".

Go for it!