Laying hens need about 16% protein in their feed. If you are feeding lots of scratch or corn you would need the higher protein since scatch and corn mess up the balance because they don't have much or any protein. I don't feed scratch or corn to my chickens as treats except in very cold weather because it helps warm them up. Hope this answers your question!
Most folks who know more than me say roosters don't need all the calcium in layer feed. The only way I could feed him something different would be to keep him separate which I don't want to do, so I'm currently taking the advice of an experienced owner who has done much research into diet. I am feeding my whole flock starter/grower and keeping oyster shell available free choice at all times. This way it is OK for younger non-laying pullets, laying hens, and roosters to co-exist. Only the laying hens will be interested in the oyster shell. They seem to know they need the extra calcium, and eat it when they need it. So far, so good. I knew it was not good for chicks who weren't laying yet to get layer feed because the extra calcium can mess up their bone development. Some folks don't worry that their roosters eat layer feed and have good results, but I imagine the effects of too much calcium for a rooster take a long time to show up.
When I do feed treats, I try to make sure my laying hens get extra protein with healthy choices like Black Oil Sunflower Seed (BOSS). It's a great treat for all the birds in moderation. Scrambled egg is another good choice or even just boiled egg yolks! If you save your egg shells and microwave them for 1 min. they will crush easily in a food processor. I make sure to give my layers plenty of them in plain probiotic yogurt weekly. The egg shells are an excellent source of calcium and the yogurt is great for their digestive tracts. The rooster and younger chicks get yogurt without egg shell. I have to put the mixture in separate bowls and give each bird the right mix. It's comical making sure the hens stick to theirs and the roo and young chicks just eat theirs! I'm glad I only have to worry about that once a week!
One needs to keep in mind that most treats will reduce the total % of proetin in the diet. Feeding a higher % of protein in the layer feed will continue to keep the level up where it needs to be for a healthy diet.