Zrog says: I don't agree with everything that's pointed out in this article/post, but it's generally correct, and for the right reasons. Note that the original author assumes that you will be roaming the support at Level 1. I've taken tips and opinions from elsewhere on the web and added them at the bottom.
By Chuavechito on PlayDota.com
You don't really need [Observer Wards] to roam but you WILL need
to counter-ward with either a set of Sentry or 1-2 Smokes. Go for Sentry
only if you are confident enough in your warding skills.
My ranking on roamers:
1) Earthshaker ("Shaker" or "ES")
2) VS [Vengeful Spirit]
3) Lich and Venomancer
4) Tidehunter
5) Sven and Ogre [Magi]
6) CM [Crystal Maiden] and Doc [Witch Doctor]
(7) [Skywrath Mage - massive mana pool and able to spam nukes].
Shaker is the best roamer because Fissure is the best roaming skill at
level 1. However he can only roam when he is picked to do so. If he
roams he will be underleveled and underfarmed so is really important
that the team picked a roamer ES and not a ES to
turtle/spam area dmg in teamfights.
Lich, VS and Veno are good roamers because they are very level and item
independent heroes. Also, their stun/slow are really good at level 1
and they have range. VS > Lich/Venom because stun > slow.
Tide is like Lich or Veno but he's melee so his ganks are much less effective.
Sven is not a good roamer because he isn't level or item independent, and has a small mana pool. [Zrog says: he does, however, have a very good Level 1 stun/nuke, and can be roamed similar to Earthshaker]
Ogre is not a good [level 1] roamer because he is very level dependent. [Zrog disagrees - he's still effective at L1, but you don't roam him at level 1, you roam him at level 3, with a 1-1-1 build].
CM is a terrible roamer because you will delay the aura too much. [Zrog just had an aneurysm, as Crystal Maiden is probably the best early roamer after Venge. If you need the aura that bad, just don't pick her as a roamer!]
Doc [Witch Doctor] is also a terrible [early] roamer because his stun is terrible at level 1. [Zrog says: that's why you roam him at L3, with 2 points in Maledict, and bring a buddy. Maledict damage is disgusting if you have someone else to dish out the first bit of damage].
Zrog's Notes:
Earthshaker and Vengeful Spirit got a lot of votes, too, especially for L1 roaming.
Treant considered a good L1 roamer with a slow (Leech Seed) + High
base dmg. L2, can dive towers with Living Armor, or can stealth with
Nature’s Guise. Should check rune early (invis, haste, DD, all good).
Start with boots, and your position 5 should
hand over some consumables.
Nyx has also been mentioned, but is less useful without levels and farm.
Shadow Demon is a good roamer, but needs a buddy for more damage. Ideally should have L3 before roaming.
Skywrath Mage hadn't been released when the above post was written, but I would add him. He pairs well with a tanky roamer that can initiate (ES, Ogre, etc).
