But now the star appears to deny his series of tweets were about the 'R.I.P' singer.
The 'Keeping Up With The Kardashians' star originally tweeted: "She cheated on me with nearly 20 dudes while we were together, I wonder how many she will sleep with now that we apart? But I mean 20?!!!"
However, Rob later reportedly tweeted: "Just so we clear I never once mentioned Rita Ora in any of my tweets."
He added: "Never mentioned any names. I speak truth. I'm a very real dude and everything I say I mean."
It was first reported the couple had split over the weekend, and Rita has since spoken out, blaming the breakdown of their relationship on the distance between them.
"I'm not going out with Rob. We were close for a while, but it didn't work because I was never there. I was like a ghost," she told Glamour magazine.
"I used to get so frustrated with myself and then wonder why I was angry, so I decided it was best to keep it friendly - especially at the moment, when there's so much going on," she added.