Infant anti-roll pillow? Safe or not?

I'm debating on getting this. Not only because my 5 week old son rolls but because he doesn't sleep well in the bassinet and I'm 99% sure it's because it's a harder surface and has no cushioning for his head. He will fall asleep on the couch or our bed in minutes but the moment he gets laid in the bassinet he wakes up and cries. So this, in theory, sounds like a great idea... but idk about the safety of it. Anyone use these?