Roster management at Ejabberd

My doubt in the form of a scenario:

A. I have 10 jabber ids in my Client's roster as well as the Ejabberd they are registered at. Now, i add 3 new User ids to my Phone's Contact list. I can see the Roster list gets updated at the Jabber Client as well as my Ejabberd server too.

B. Now from the list of 13 users/jabberd Ids, i delete 4 contacts from the Contact list of my phone. The Ids get removed locally from the roster maintained at my Jabber Client. However, how is this deletion-related management done at the Ejabberd's end?

Are any explicit calls to the roster modules requierd for updations at the Ejabberd server? If so, what are they?

Kindly let me know! Thanks