12:10 PM PT -- Mike Tyson is out of the Ric Flair roast ... after signing on to participate in the event.
"Due to unforeseen circumstances Mike will not be participating in the roast," Iron Mike's reps told us. They did not wish to elaborate.
Before Ric Flair doles out one last ass whoopin', the WWE legend's gonna take a few (verbal) jabs from Mike Tyson -- 'cause TMZ Sports has learned Iron Mike will be one of the celebs roasting Nature Boy this summer!
We're told 55-year-old Tyson has signed on to be part of the roast of 73-year-old Flair ... going down July 29 in Nashville, TN ... in front of over 1,000 fans!
Ric and Mike -- two of the absolute greatest in their respective fields -- aren't just buddies, they're also business partners.
In fact, Mike's "Tyson 2.0" cannabis company recently struck a deal with "Ric Flair Drip" ... and the men will be selling different marijuana products (think edibles, etc.)
And, Tyson won't be alone in roasting the 16x world champ ... Starrcast, the company behind the event, tells us they're in the process of locking down other celebs and wrestlers for the roast.
If Ric makes it through the roast, two nights later he's scheduled to wrestle in the final match of his incredible career. His opponent is still being sorted out.