Ashlee Jenae's fiancé Joe McCann is speaking out for the first time following her sudden death while the two were vacationing in Tanzania.

Joe took to social media -- after not being heard from as the investigation into her death over seas left him without a passport -- starting his message with, "There are no adequate words to describe the total devastation, emptiness, and shock I feel after losing my best friend, confidante and fiancé, Ashly Jenae Robinson."

Joe continues to say "As a father myself, I am also heartbroken for Ashly's parents, Yolanda Endres and Harry Robinson. Ashly's death is an incomprehensible tragedy."

Ashlee's fiancé solemnly adds ... "What Ashly desired most was to become a mother and to raise a family together. There is no question that she would have been an amazing mom."

As we previously reported ... Ashlee -- real name Ashly Jenae Robinson -- was reportedly found unconscious in her villa and rushed to the hospital, where she was ultimately pronounced dead, all during a trip she and McCann took to Tanzania last month ... just days after he popped the question.

According to local outlets, police were initially leaning toward suicide ... but her family isn't convinced, and is conducting an independent autopsy to try and get answers.

As we previously reported, her body was returned to them about a week and a half ago ... but Ashlee's dad told us they hadn't gotten her belongings back -- including her engagement ring.