Hi rasmy - Take a look at this chart. It may help you as a guideline to desired weights for the Rottweiler.
http://www.rottweiler.net/forums/sho...tweiler+by+age
Every dog has a different metabolism, activity level, etc., so that plays into what they'll weigh. Your boy is lean, and that's great. He'll have alot less joint stress by not lugging extra wt around. My girl filled out in her 2nd year, and even more as she approaches her 3rd birthday. She has highly defined musculature, and is lean, but we're very active.
kathy