Side sleeper

So obviously back is best but I know when baby can roll into their side/tummy, you’re supposed to let them. However, my son isn’t even 3 weeks old (36+3 adjusted age) and he rolls to his left side every time I lay him down 😫 he is able to go back to his back when he wakes but I cannot keep him there as he tries to fall asleep. I’ll wait until he’s in a deep sleep in my arms, lay him in the bassinet, and he rolls to his left EVERY time.

In the nicu, they had this little cozy thing they strapped him in to keep him on his back but got rid of it and let him sleep in his side as soon as he moved to an open crib. He had all kinds of monitors on him to make sure he was okay though 😫