You are doing what I normally do - eventually once they get older they realize that they can return to sleep without 'crying out' when they roll over and wake up - we all often wake several times a night we just do not remember it cause we return quickly to sleep.

The only thing I could add to what you are already doing is perhaps a 'sleep sack' to help keep him feeling secure through his sleep - it is a way to 'swaddle' kids who are more mobile than a younger infant?

Sleep Sacks

I have had two kids in my home career who have a very high anxiety for sleeping in 'cribs' and one I could not even get to sleep in one and the other would go in if you rocked him to sleep but after 30 minutes he would scream - both ended up having to move them even as an infant to a toddler cot and put them in the main floor living room where I spend quiet time to 'watch' that they stayed on it or if they were rolling around to make sure that they stayed in the middle (it is only 2 inches from ground but still do not want them rolling off it if possible) but that move allowed them and I to immediately get a nice 2-3 hour nap without 'crying out' in between cause they roll over see they are not 'alone' in a pen and go back to sleep within 30 seconds - no noise to wake up others in the house .... sleep is important to me and I am willing to think outside the box a bit to help ensure they get it - both these children also 'co sleep' at home so I think the being 'alone' in a room was the biggest issue for them... for me it was easier solution than trying to 'break' them of the habit while listening to them scream for weeks over nap time - got me the end result I wanted immediately - a child who self soothes to sleep on their own ,,, and eventually they grew out of needing to 'see me' while they went off to sleep and i slowly move the cot toward where the other 'cot nappers' are.