Ronda Rousey -- I'm Down For WrestleMania, IF...

"Rowdy" Ronda Rousey is totally down to get in the ring with the WWE's finest at WrestleMania ... but she'll only appear with her posse.

Rousey and her roommate/UFC fighter Shayna Baszler posted a video of the two mixing it up in the ring last week -- the rumor mills went wild ... and we're told she'd be stoked to wrestle a legit match at WrestleMania.

Sources close to Ronda say she's busy with movies and real fighting ... but if WWE honchos wanted to make it happen they can get the ball rolling by hiring her crew -- the Four Horsewomen -- Baszler, Marina Shafir and Jessamyn Duke.

We're told the fighter is saying WrestleMania XXX in New Orleans next month would be out of the question ... but if the WWE is interested, she'd be down to make it happen at next year's event in SF.