Ya if you start close to Rome, you have to expand somewhere to get an advantage over them. Idk if Syracuse starts with phalanges, but you need extremely quality heavy infantry with support bonuses to hold them off.
In my last playthrough I avoided war with Rome for as long as possible, and had Gothic Heavy Infantry (which is pretty OP) and cataphracts to go toe to toe with them. Even though, if it had not been for a long series of really bad civil wars id probably just be equal with them.
Units which will probably help off the top of my head:
-- Any Phalanx
-- Gothic Heavy Inf
-- Dacian Heavy Inf
-- The Belgae Heavy Inf (I forget the name, provincial unit, same as the others)
-- Cataphracts
-- Archers (as opposed to other slinger/skirmishers)
Try to avoid medium infantry, as Rome, and other powerhouses, will slaughter them. Definitely try to reduce combat width, as they have large armies. Although, as long as you dont fight on plains, neither side will be able to use the full weight of their army, so quality is often more important.
As my empire grew, I pretty much had to tank the expenses and use mostly heavy infantry as my main frontline unit, especially named heavy infantry. Although, in some instances Cataphracts can be more devastating.
As for useless to play factions near Rome, the Italian Peninsula is tough, but (in Sicily, Iberia, or Illyria) if you can diplomicizetm well, you just have to wait them out as they'll inevitably get into other wars/revolts. Be warned, from my experience they'll most aggressively pursue their objectives in African Carthage and Illyria/Balkans.
To exacerbate the whole problem, if Rome doesn't get into historical or a-historical bloody conflicts early on, they can definitely snowball hard--although again, if they stagnate expansion-wise, you'll most likely get some space. Italy always seems like its ready to revolt.