Hi Shoegal,
we have like a safe t sleep in our cot to actually stop Benjamin rolling around.
The one we use is ALOT cheaper than a safety sleep and is actually a goldbug safe changer, but with the straps extended it goes all the way around the mattress.
It clips up around his waist and he cant go anywhere, we actually got it though cause of his reflux wedge, he scoots down the bed otherwise!!!