I am aware of how Rome preferred to make a vassals instead of allies. However I would imagine that in the early parts of it history it would not have the power or authority to subjugate. Im thinking of an alliance network Rome may have had perhaps with germanic tribes?
I don’t know if I would compare it to NATO, but Rome had plenty of allies throughout its history. The closest example to what you’re asking would likely be the alliances that the Roman Republic had the cities of Latium, and then later on the non Latin italic people’s.
Anyone who was from Latium had “Latin” rights. Which meant you could freely move from city to city and you would be a citizen of your new city. You could marry anyone from any other Latin city. And merchants could trade in any Latin city (there might be more that I’m forgetting at the moment). As Rome grew more powerful, in the early days of the Republic, and became the most powerful City-State in Latium they formed an alliance with the “Latin League”. This was an organization of other tribes and cities in Latium, and they promised to send troops to serve with the Romans in battle. In exchange Rome would share any loot with the rest of the Latins.
The rest of the Latins began to fear the growing power of Rome, especially as they were now relatively safe from outside invasions. Eventually war broke out with the Latin League fighting against Rome. Rome managed to win and then renegotiated its alliances with the rest of the cities of Latium. Except this time they signed individual treaties with each city rather than one treaty that applied to everyone. This allowed Rome to offer terms that would better suit each ally, instead of one universal set of conditions.
The situation with the italic people’s was somewhat similar to this. Rome had treaties with a large number of the different Italic peoples throughout Italy. The Italics however began to grow weary of what they viewed as unfair. They wanted Roman citizenship and the same rights that the Latins had. Marcus Drussus, who was Tribune of the plebs, attempted to pass reforms that would extend citizenship to the italic allies but he was assassinated. This was the last straw for most of the allies and they rebelled. Rome once again emerged victorious, this time they did so by offering citizenship to any of the cities who surrendered.
I know this had more details than just describing the nature of Rome’s alliances but I figured I might as well go the whole nine yards with it.