Who are some minor characters in Romeo and Juliet, and what's their role/function?i

A good place to start would be with the servants Sampson
and Gregory (from the Capulets) and Balthazar and Abraham from the Montagues.  These
characters are both significant and interesting because Shakespeare uses them to set the
tone in Verona in Act I, Scene I.  The fact that these four are mere servants to the
families, yet they take it upon themselves to carry on the pointless grudge shows how
deep rooted the feud is.  Without these periferal characters continuing to spark the
rivlary, it may have ended long ago; however, their hot-headedness and dogged loyalty to
the families rile up the entire town and rekindle the ancient rivalry.  It could be
argued that without these minor characters scuffling in the street,  the Prince would
never have had to enact his new policy of death to the next person to commit violence. 
Without this law in place, Romeo and Juliet wouldn't have been faced with the dilemma
that fell in their lap after Romeo killed Tybalt.