"The ability to monitor a replication topology is restricted to the sysadmin fixed server role, the db_owner fixed database role, and the replmonitor fixed database role on the distribution database. You can add users to the replmonitor fixed database role programmatically using system stored procedures."
For more info, look up "Replication Monitor" in BOL. There is a lot of information in there.
Author - Professional SQL Server 2005 XML