The easiest way to rove is to wander around the reference areas paying particular attention to patrons who appear confused or who the librarian knows from prior interactions needs extra help or are working on a tough research question. Another thing to notice is if patrons are not doing research in the most efficient manner. A patron who is at record 13 of 2013 on a research database certainly needs some rover intervention. After identifying patrons in need of help, the librarian must strike up a conversation with the patron. The choice of the initial question is particularly important.
Patrons can be sensitive about appearing dumb.
This is why many of them do not go to the reference desk in the first place. It is important not to phrase questions as if the patron needs help. Many patrons will immediately get defensive. Another point to remember is that some patrons do not want to be approached. If the librarian feels the patron is uneasy with being disturbed, the librarian needs to end politely the rover encounter.