Michael Sam & BF -- When In Rome ... Make Kissie Faces

Michael Sam is leaving the harsh world of NFL rejection behind him ... jaunting off to Europe for a fun-filled kissy-faced vacation with his BF Vito.

The love birds have been posting pictures to Instagram like crazy from spots like Madrid, Rome and most recently The Vatican on a multi-country trip to celebrate Sam's 25th birthday.

Sam believes the fact he's openly gay is a factor as to why he's not on an NFL roster -- but it's clear he refuses to compromise the way he lives his life for a shot to make it in the league.

You know what they say -- When in Rome ... stick it to the haters.