Strap him to the bed with bungees or similar have you tried under inflating the airbed so it just supports him off the ground as this can help or change the airbed for a SIM as not so far to fall
------------- Experience enables you to recognize a mistake when you make it again.
Everything has been said before, but since nobody ever listens we have to keep going back and saying it all over again and again and again
Ours roll off single airbeds too so we bought them a double to share which stopped them rolling off but caused fights ! Tried camp beds but didnt get on with them. Now I put a quilt/blanket on the floor so if they roll off they don't get cold and wake up, it works fine.
Think I'll use an ordinary air bed, under inflate it with a blanket next to him just in case. Have space for a double for him, so may consider one of those.
My Daughter has always slept really well on her single air bed with no problems at all! My Son is just too much of a fidget!
I say a double self inflating mat if it fills the whole bedroom, nowhere to roll off to then. He would only need the 3 or 5 cm mat so not to bulky or to much money.
Gary
eeeeh air beds when I were a lad we slept on ground with an old army blanket between 6 of us
Seriously everyone is right don't inflate so much it shall provide a dip in the middle the only other thing to try is put some stuff under the air bed at each site to raise it slightly at each side.