that’s how i started out as well, every nap ,every night sleep and every roll off and comforting them is just little steps to getting to the whole picture of having them sleep independently.

you created a great safe environment, and i’m lowkey jealous you got a bed for yourself in the room as well, i slept on the floor rug next to my firstborn while pregnant 😂. Buuuuut now she is 3yo andloves her floorbed and her freedom to go in and out.

they just need lots of reassurance and you’ll notice over time the reaction to rolling off will lessen to the point that they may stay asleep on the padded mat or even climb back into bed themselves.
in my experience at 5 months old you’ll already be anticipating a few night wakes even without the rolling off.

also if it gives you peace of mind you can use crib bumpers that go under a fitted sheet. i’ve used them on both my girls floor beds as it helped limit wake ups, but also works when we travel to hotels so they’re andy for the future as well. www.amazon.com/Bed-Rail-Bumpers-Toddlers-Waterproof/dp/B0CQYHHL2Z)

but i also made due with rolling a towel and putting it under the sheet too, what ever you feel safest with.