The former Cheetah Girls star and Kim Kardashian's younger brother dated for two years until calling it quits in 2009, but he has found love again with Kim's former friend Blac Chyna.
Rob and Blac announced their engagement on social media on Tuesday (05Apr16), and Adrienne has now revealed she harbours no ill will towards her former flame.
"I think everybody deserves happiness and I think it's just absolutely awesome," Adrienne told E! News. "He looks like he's so happy."
Blac's ex-fiance Tyga, with whom she shares three-year-old son King Cairo, recently expressed a similar sentiment to Adrienne.
The hip-hop star, who is currently dating Rob's younger half-sister Kylie Jenner, took to Twitter shortly after the engagement news was confirmed and wrote, "Everybody deserves 2 be happy. What some1 does for their happiness is not my concern, as long as it's not interfering wit my happiness. It makes me happy to see the mother of my son happy (sic).
"My only concern in this situation is my son. I want him in happy environments. He's innocent in this. & I want him to feel as much love as possible. Only an evil heart would direct negativity at a child & make fun of him for being in a situation that is out of his control."
He concluded, "When u been blessed how I've been, & create some1 u love unconditional, u'll (sic) understand how I feel. U'll want to protect that blessing. Cherish yo own blessings and stop hating mine."
Tyga and Blac dated for three years before splitting in 2014.