Some birds will call and await a response. In this situation, responding to the first calls might have stopped a screaming episode before it started. So if you can figure out what starts the screaming, or some of the screaming, sometimes you can stop it before it starts. You mentioned Romeo screams at all unfamiliar objects or people. This sounds like at least some of his screaming may be due to insecurity.
Some birds are more cautious about new people or objects in their environment than others.
Introductions to these should be gradual and very non-threatening much like you may read recommended for African Grey parrots. To introduce a new object or toy, first place the object somewhere in the room but not close to him. Somewhere where he can see the object from a non-threatening distance. Leave the object there for a few days. Move it a bit closer, wait a few more days.