Are you both quite sure?
I'll admit I'm almost clueless about breed characteristics, but I've been reading up and learning. I've learned that the APA standard for Rhode Island Whites IS a rose comb, but there are strains that have single combs, like this one from Cackle Hatchery:
https://www.cacklehatchery.com/product/rhode-island-whites/
So.... it *could* be either breed? (Just not a Leghorn.)
I've also read that the White Rock is most commonly used for commercial egg production, weighing up to 7.5 lbs. The Rhode Island White is a newer breed, hardier, and most often kept in backyard flocks; weight up to 6.5 lbs.
So... I still think it's a Rhode Island White, due to apparently coming from a backyard flock. I could very well be wrong, though. If I AM, then please correct me so everyone can learn, and I won't perpetuate false information.
OH! And to
@TripleH23, where did your seller get this bird? That might be your best clue.
And THIS great tidbit, if it IS a RIW:
I read that crossing a RIR hen with a RIW rooster produces sex-linked chicks! Pullets will be red, and cockerels will be white. Bonus! For this alone, I truly hope he is a Rhode Island White.
(I'm not inclined this morning to post all the links from where I garnered this information, but I will if anyone here thinks it's necessary. Let me know.)