So I'm going to try my hand at this. I'm going to look at all the heroes not in Dota 2 yet and tell what role (s) they are.
Phoenix - 3-5 role. Support/teamfight. His skills could be useful in a lane, particularly a trilane with a stun. There is a straight up Wombo Combo with a Naga Siren and that ultimate.
Legion Commander - 4-5 support, more in the vein of Abaddon. The ult can basically keep someone disabled and is a great banking tool if your team will back you up. I could see going Blademail for those troublesome right clickers.
Earth Spirit - mid or offlane, 2-3. He seems to be able to control his lane well as well as have good ganking potential. He also has an escape, making offlane work out.
Ember Spirit - 2, mid. Good lane control and good ganking at 6
Techies - This hero sounds broken as hell. I guess he could be a mid though. His nukes (understatement) ramp up nicely in a solo lane. 300 damage mines at level 1 is RIDICULOUS though.
Oracle - definite support, 4-5.
Pit Lord/Abyssal Underlord - 3-5. Has potential at mid, but also could excel at support in a lane. The rotation ability is like a super Io though. I can see wombo combos of this with a Centaur.
Terrorblade - 1, hard carry for sure. His strength gain doesn't look that great, so I imagine he might want a Heart.
Arc Warden - 1-2, carry. You have the right items for him and you are looking at some insane potential. He's like a super Meepo that you only have to micro 20 seconds at a time and only the main one absolutely has to live. Diffusal and Manta on this guy has serious potential.
Winter Wyvern - very much a 4-5 support.
Edit: something I didn't even think about on Arc Warden: there is practically no reason not to go Midas on him. Even if you don't get it by 7-8 minutes, it will pay for itself every time you use your ult.