I found some interesting information about the Rosato brothers in the screenplay of The Godfather II. First, the conversation Mike had with Roth at his home which was apparantly cut or shortened in the film. Second, the conversation of a deleted scene where Pentangeli meets with the Rosato brothers for the first time (see picture).

It explains and confirms their role within the Corleone family.

The conversation between Mike an Roth:

MICHAEL
The Rosato Brothers have performed
services for you in the past; I
understand that they are under your
protection.

ROTH
(simply)
We do favors for each other...

MICHAEL
Technically, they are still under
the Clemenza wing of the Corleone
Family, now run by Frankie
Pentangeli. After Clemenza died,
the Rosatos wanted territory of
their own. Pentangeli refused, and
came to me, asking for permission
to eliminate them. I, of course,
knew of their relationship with
you, and in gratitude for your help
with the Tropicana matter, turned
him down. Pentangeli was furious,
and paid one hundred and fifty
thousand dollars to have me killed.
I was lucky and he was stupid.
I'll visit him soon.
(leaning toward the
old man, sincerely)
The important thing is that nothing
jeopardize our plans, yours and
mine. This thing of ours, that we
will build.

The old man touches Michael's hand, warmly.

ROTH
Nothing is more important.

MICHAEL
(quietly)
Pentangeli is a dead man; do you
object?

ROTH
It's always bad for business; but
you have no choice.

MICHAEL
Then it's done. I must choose his
replacement: it cannot be Rosato.

ROTH
Of course you must keep control of
your family.

The first meeting between Pentangeli and the Rosato brothers.



INT. THE RESTAURANT - DAY

The restaurant is quite empty, despite the excitement out on
the street.

Pentangeli immediately sits at a table with a tall, dark,
snappily dressed young man, CARMINE ROSATO.

Nearby, on the other side of the room is Rosato's brother,
TONY, seated with a group of their men.

At another table in the restaurant is a table of Pentangeli's
people: they are joined by bodyguards.

PENTANGELI
Rosato, where's your brother?

ROSATO
Sitting right behind you.

Pentangeli glances behind himself.

PENTANGELI
He don't want to talk?

ROSATO
We worked it all out beforehand.

PENTANGELI
Are we going to eat or what?

ROSATO
Sure, on me. I got Diner's Club.

PENTANGELI
(sarcastically)
Forget it; I'm suddenly without an
appetite. You're making big
trouble, Carmine.

ROSATO
You weren't straight with us,
Frankie, what else could we do?

PENTANGELI
We could have talked first, saved a
lot of running around.

ROSATO
You wasn't listening, you didn't
want to talk.

PENTANGELI
Don't I look like I'm listening?

ROSATO
We want Brooklyn one hundred
percent. No more taxes to you. We
want to be only loosely connected
with your family -- sort of a
under-family all of our own. Then
we can act on all internal matters
without talking. Also we want you
to inform Michael Corleone that we
can deal directly with him.

PENTANGELI
I'm a little hungry, maybe I'll
order something. Joe.
(one of his men)
Get me some bracciole or something.
And pay cash.
(to Rosato)
And in return for these concessions,
what do you do for me?

ROSATO
We will release the hostages,
number one. Number two, we're here
for you to count on when you need
us. We're independent, but we're
here if you need us. In general,
we'll cooperate with you and your
businesses, and you in turn will
cooperate with us. Pari persu.

PENTANGELI
Pari Persu; what the fuck is Pari
persu...?

ROSATO
My lawyer went over this beforehand.

PENTANGELI
What assurances do I have that
there will be no more kidnapping,
no more hits?

ROSATO
The same assurance we got from you.

PENTANGELI
What if I say shove it?

ROSATO
Then Carmine Fucillo and Tony Blue
DeRosa will need to be fitted for
slabs.

PENTANGELI
You want a war?

ROSATO
We got no choice.

PENTANGELI
You know if there's a way I'll go
to the commission and the commission
will side with me. That puts me
and the other New York families
against you.

ROSATO
We got friends in the commission.

PENTANGELI
(getting angry)
I'm talking about Italians!

ROSATO
What about Michael Corleone?

PENTANGELI
He supports me.

ROSATO
Maybe, yes... maybe no.

One of Pentangeli's men approaches with a plate of Italian
food.

Pentangeli stands up, angered by this remark of Rosato's; he
pushes the dish of food out of the surprised Bodyguard's
hands.

PENTANGELI
You drove old Pete Clemenza to his
grave, Carmine; you and your
brother. Turning on him; trouble
in his territories -- you and your
demands. I hold you responsible,
just as though you shot him in the
head. And I ain't gonna let that
go for long!

Pentangeli walks out of the restaurant; there's a little
tension between the bodyguards of the two factions.

ROSATO (O.S.)
Hey, Five-Angels...

He gives him the arm.

Frankie's face turns red, like he wants to have it out here
and now; but Willy Cicci calms his down, and they all make
their move out.

EXT. THE RESTAURANT - DAY

Pentangeli gets into the car.

PENTANGELI
Nobody I hate calls me Five-Angels
to my face!

He slams the door.