Collin Stewart hit four 3-pointers and finished with 17 points for Monmouth (17-5, 9-2 Metro Atlantic) which has won eight of its last nine and maintained a one game lead over Sienna in the MAAC standings.
Quadir Welton scored 16 points and grabbed 11 rebounds to lead the Peacocks (8-11, 6-4), who after starting 6-1 in conference play has dropped three in a row.
Antwon Portley added with 10 points for Saint Peter's.
After trailing by 11 at halftime, a Welton layup for Saint Peter's cut the Hawks lead to 62-57 with 5:25 to play. But from there Robinson erupted, scoring all nine points of a 9-2 Monmouth run which extended the lead back to 69-57 and effectively put the game away.