Well, I don't have Rotties, but I do have pitties who's coats are quite similar...shiney, short, course if you pet them the wrong direction...To keep my dogs' coats soft, shiney, and beautiful, the first step is to NOT OVER_BATHE them. They have sensitive skin that will dry out and dull with too many shampoos no matter what product you use. We use oatmeal shampoos for dogs as adults and puppy shampoo for puppies. We bathe them about twice a year unless they get really dirty and it doesn't wash off with spraying them down with a hose. Only batheing them twice a year helps to ensure they keep those natural oils in their skin which also ensures a shiney coat. The oatmeal shampoos also help to not take the oils out of their skin when they do get baths.
In addition, we add Linetone to their food about once a week...this also helps to keep their coats soft and shiney...people are usually amazed how in just two weeks, a rescue's coat can go from gritty and dull to soft and shiney using the oatmeal shampoo and Linetone in their food. My dogs feel like "Pound Puppies" (those stuffed dogs many of us had as kids, I had a few myself) Both Linetone and Oatmeal Shampoos are easily gotten at Petsmart. Follow the amount instructions on the bottle of Linetone so you know how much to give each dog (amounts vary due to size of dog)
As far as the dead skin and scab issue...My guess is that is what it is, but I can't be sure without seeing him...when my dogs get something like that...we make sure the scabs stay clean, but other than that, leave them be to heal and fall off on their own. You can ask the vet about it if it's not gone by his next appointment, or if you would feel more comfortable, call your vet and tell them the situation and ask about it for a professional opinion