Very nice looking horse! MAY be a bit over at the knee, but it is hard to tell on soft footing and that is not a fault to worry over. I Love his nice low hocks and he has a very nice topline. His lumbosacral joint is set a bit far back.. but at 16 if he looks this good, don't worry over it. You have a very nice horse here.
This horse reminds me on some levels of this horse, Lonrho. I have used him before as the horse with ideal conformation. Look at the hind leg conformation of your horse and this horse. Very similar. You can see this stallion has a little better coupling (and NO he does not have a roach back.. he has a correct and very STRONG back).
BTW here is Lonrho's pedigree: Lonrho Horse Pedigree