I am somewhat in agreement with Chris but, 1st of all, you have to take my thoughts with a grain of oyster shell since I haven't had a rooster for years and years.
The ag agency for Ontario has some thoughts on roosters eating, "high-calcium breeder diets, which provide 4-6x their calcium needs." They report that, "kidney dysfunction is quite rare in these birds."
Pre-Breeder diets (click)
Keep in mind their audience for this advise: commercial outfits that will only keep those birds as long as the hens are in full production. The roosters will go when they cycle that flock out of their operations. If you wish to have your roosters over a long time and are concerned about their kidney health especially, you may not want them eating the same feed as those egg-a-day layers. And, it is those kidneys that have to deal with all that extra calcium. If they cannot, it builds up within the bird.
An easy thing to do is feed them all something like Flock Raiser and offer oyster shell, free-choice. There is a current thread on this forum "Flockraiser for Laying Hens" for you to read what others do. You can also
dilute the feed the rooster gets by giving him extra scratch grains or kitchen scraps, separate from the hens. He not only doesn't need so much calcium but he doesn't really need all the protein either.
And then, if you take my thinking on this completely -- that rooster is just lucky to be hanging out with a flock of laying hens, anyway
.
Steve