Just to bump the thread and get things going

Death Prophet
Noob Role: Nuker

I just played a few games as Death Prophet and she is really strait forward. your Q is your bread and butter your third skill is a passive making everything better and your ultimate hurts, is easy to use , heals you at the end, and can help take down towers.

Useful guide: http://www.dotafire.com/dota-2/guide/new-ish-players-guide-to-death-prophet-1254#chapter1

A lot from the secret shop and a bit pricey but you are unfair after getting all of this

*Edit*

Venomancer
Noob Role: Support

Venomancer makes wards that attack, slows and places two different dots on players making him a great assist on kills and helping push a lane. You could also play him as a pusher but support is easy sit back get a dot on heroes and place wards

Useful Guide: http://www.dotafire.com/dota-2/guide/support-pusher-venomancer-guide-1429


Undying
Noob Role: Initiator

Undying is a lot of fun and a great add to a teams durability. with a heal and strength drain moves he can sway a battle. To me Undying's best asset is his third ability that summons zombies at all enemy targets they slow and count to your last hitting gold wise making farming a big way easier. All his health gain makes him easier to learn because he can survive so give him a try.

Useful Guide: http://www.dotafire.com/dota-2/guide/how-to-dirge-the-undying-1372

This is the guide I use I found it good so I would give it a try