Want the concept, don't worry. For free, but just for you.
So in this alternate messed up universe where the Potara is permanent. I know right, crazy. But the weirdest part is that there isn't a double voice for fusions, super weird. Now back to the actual serious part, Goku and Vegeta never defused, they became a single person. But as all people do, Vegito died, yes he's dead. But don't fear for he has reincarnated! You! The reincarnation of Vegito.
So, in most Dragon Ball and RWBY crossovers, they make it so that the Goku and Vegeta are sent to Remnant, which is the Earth of the universe. But me? I'm different gravy, so I've decided to make Earth and Remnant two different planets, same universe, but the planets aren't remotely near each other.
Now that you know about Remnant and Earth, it's time you learn about planet Vegeta in the universe. When it was destroyed by Frieza quite a bunch of Saiyans were sent to Remnant because of its history of being a rough place so Saiyan parents thought Remnant would be home away from home. Where their children would have a pretty similar life almost like they were raised on Vegeta.
YOSHA! Let's check it out!
(Also if you couldn't tell there's gonna be repeated use of the term, phrase, whatever the heck you wanna call it, Y-O-SHA!)