Is it likely that a bmx chainring will fit on a road bike?

No.

Some BMX chainrings have the same 4/5 bolt pattern as road bikes, but most use another method of attachment to the crank.

If it is a 4/5 bolt chainring you first have to measure the bolt circle diameter to see how that fits. I'll post a link on that.

Next is the thickness of the chain rings. BMXes are single-speed and use a thicker chain. Most road bikes have external gears and need a thinner, more flexible chain to work. I'm not sure if a road bike chain will fit on a BMX chainring.

(Unless it's a single-speed road bike of course. Then you can run a BMX-style chain and all can be made to work.)