How to widen a regular iron frame bed?

You can only really make it as wide as your mattress. Are you planning to buy a new mattress?

Maybe a different solution would work and be less expensive. Here's a "bumper" from Amazon.

https://www.amazon.com/Milliard-Non-Slip-Hypoallergenic-Resistant-Washable/dp/B0748XPZHR

There are also other types of guards available.The article is titled for "seniors" but will work for anyone. This might be worth taking a look at:

https://www.homecareassistancesacramento.com/how-to-prevent-elderly-from-falling-out-of-bed/

Why not just buy a new frame besides if you need more room you would have to buy a new mattress to fit the bigger frame.

Hello. It sounds like you need a new larger mattress.

You can change the rails and replace with queen extenders. Then put a queen box springs and mattress on the bed. I have done it with 3 different bed frames and it doesn't look odd since it basically brings the mattress slightly out past the edge of the headboard on most, 1 of them it only came mid-edge because it has a large head & foot board.

Was wondering if there is a reason you keep rolling out of bed and onto the floor, it might be the width of the bed or is there something else going on? You might be just restless when you are asleep. Lots of speculation has been written on this topic, you might research it.

To eliminate half of the problem, can you put 1 side of your bed up against a wall?

Here is a link with info that might help you:

https://sleepsugar.com/stop-rolling-in-your-sleep/

They make bed assist rails (like those on hospital beds).