Salve, Beyard,
I'm always glad to see more people interested in Roman history and Roman personae. I'm basically the biggest Roman history nerd in the world, and am personally glad to see more Romans on the field. After all, we
do deserve to rule the world. I mean, who else can do it as well.

I have a few comments on the garb links you posted, some hints on how to do a successful Roman unit, and some helpful links for you.
First off, regarding the links you posted from Dark Knight Armory:
* As several other people have said: skip the leather helmet. A Roman, and especially a Roman commander, represents the dignity and majesty of Rome. I've seen that particular helmet, and to call it a flimsy piece of crud is overgenerous.
* The metal helmet looks a little better. That hollow visor, however (the protruding piece over the brow) is simply a thin piece of metal bent into an L. It
will bend and break, rapidly. Look for a helmet with a solid visor or be prepared to take that off when it breaks. Also, bear in mind that historical Roman helmets go beyond the Imperial Gallic style: I'd personally love to see some Coolus or Montefortino helmets on the field.
* The caligae (sandals) look pretty decent. They'd make good feast garb, but I, for one, would never, ever fight in sandals. Romans are usually to be found in the heaviest shield wall scrums, pushing and shoving and generally kicking hell out of their opponents. Historical accuracy be damned: for fighting, I wear sturdy leather boots with good traction and ankle support. Your unbroken toes will thank you.
* Lorica segmentata is very nice armor to wear. It looks fantastic and distinctively Roman, offers good protection, and is remarkably flexible for plate armor. That particular segmentata looks, well, bad. I mean, going by the picture, the chest plates are bizarrely different sizes and completely fail to overlap. It's either bad armor or the worst marketing picture I've ever seen. If you do wear segmentata, be prepared to get really good at fixing it. The straps and rivets where the four pieces join together were a weak spot in Roman times, and remain so today. You will blow out hinges and rivets, and you will have to fix them. Again, and again, and again.
* Bear in mind as well that, Hollywood notwithstanding, Roman legions were not especially uniform in armor. It's entirely appropriate for legionaries and centurions of any period to be found in chain, segmentata, and even scale, as well as wearing a mix of helmets. The historical case for officers in lorica musculata is less strong, only attested in carvings. In Dagorhir's Rome, we reserve musculata for citizens only.
* Badassgarb or one of the other estimable Dagorhir vendors can make you a nicer Roman tunic than that for the money. One thing to keep in mind when designing your unit's uniform - the case for red tunics on roman soldiers remains hotly debated. You don't have to have red tunics to look Roman, but you should settle on a uniform look.
* The belt. Romans wore belts, yes. That is indeed a picture of a belt. If you want a more historically accurate look, try a cingulum (also called a balteus). For fighting purposes, many Dagorhir Romans wear what we (inaccurately)call pteruges - basically, a belt and skirt of armor grade leather flaps that covers you from the bottom of your lorica to the top of your greaves, which are also recommended for game purposes, even if they weren't issued to every legionary historically.
Ok, now a few tips on how to make a successful Roman unit. Bear in mind, these are my personal thoughts on the matter. It's your unit, do it how you like.
* If you're going to be Romans, fight like Romans. Romans are soldiers, not warriors. It's an important difference. We look alike, use a standard set of weapons, and maneuver and fight as a unit. If you wander out on the field with some guys with sword/shield, some dual wielders, a couple of greatsword guys, and some assorted polearms and then rush off in all directions and get waxed, people will say "Hey, look, a bunch of barbarians in captured Roman gear."
This takes practice. When you get together for unit practices, don't just spend time fighting. Learn how to work together in teams. Practice forming a line, advancing, wheeling, charging. Establish a command structure and make sure everyone understands it and what their job is. Stay together, move together, and for Jupiter's sake, attack together. Piecemeal Romans are dead Romans.
* Look like Romans. That means uniform garb and equipment. Everyone should wear the same color tunic (as above, not necessarily red). With the exception of a few support weapons, your weapons should be javelin, short sword, and scutum. You don't necessarily have to have everything right out of the gate, but it's a good goal to work towards. It helps establish discipline and esprit de corps, which is a good part of what differentiates a group of soldiers from a warband.
*Behave with dignitas. When you take the field as a Roman, your behavior reflects on all Romans. Play fair. Be a good sport. Don't rhinohide. Don't be a jerk to people - everyone's out here to have fun.
Contribute to the game, and to the good time of your fellow players. When someone quotes Monty Python ("What have the Romans ever done for us?") they should, on reflection, be able to come up with a good list of stuff to answer it with. You know, roads, education, water, law and order, keeping the peace...

Finally, here's a few links I've found to be helpful. Some are primarily history, others are excellent resources for making historical kit or adapting Roman culture to the modern world.
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http://larp.com/legioxx/ - One of the best resources I've found for historical Roman kit. These guys are living history reenactors, and they take it seriously. How to make everything Roman you could ever want.
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http://www.livius.org/rome.html - Roman history.
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http://www.romanarmy.com/cms/ - more Roman history, with a focus on military matters. They have an excellent forum.
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http://www.novaroma.org/nr/Main_Page - a group dedicated to bringing back the Roman Empire (or at least, to reviving Roman culture). I've been a member, and now I'm not. Their website is goldmine of resources. Their group culture, I found to be...acrimonious. They make folks on these boards look like gentle little lambs.
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http://www.armourarchive.org/ - several other people have mentioned this, but it bears repeating. Almost everything you ever wanted to know about armoring, and a good classified section, too.
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http://thehistoryofrome.typepad.com/ - an excellent and entertaining Roman history podcast, from Aeneas to Romulus Augustulus. Check it out. If you like Roman history, you'll love it.
Well, now that I've run my mouth at great length, let me say welcome, fratre, and good luck with your new unit! If you have any questions, or if I can help in any way, please ask. I read these boards regularly, although I post infrequently. You can also find me (Peter Ponzini) on the Tome of Faces.
Ave atque vale!
Gnaeus Pompeius Rufus
SPQR