I don't advise this. I've never owned either species, but I read that Rosellas are known for being territorial and aggressive. On YouTube, Donna at "Love of Pets" (one of the few YouTube creators who I still respect) also mentions their bossiness. Granted, there are things that people say about any species, which are not always true about every bird.
However, it's always risky to combine two species. Some owners say they have no problems, especially if the birds grew up together. I believe that a bird appreciates some time to be alone or with others of the same species. Many people combine Budgies and Cockatiels, both of which I have, but my Cockatiels seem to want a break from the Budgie excitement at times.