Hero Roles
All heroes in Heroes of Newerth are unique when compared to each other skill-wise, but many of them fall in to the same category in which role they should perform for their respective teams. It is very important when you choose your hero that you understand what role you will be playing for your team. If you attempt to undertake a role that your hero is not meant for, your team mates will often feel they are playing 4v5 as the usefulness of your hero will drop immensely. Another very important thing is to make sure you look at the make-up of your team before you pick a hero. Don't pick a carry if you see that two or more of your team mates have already picked one. Conversely, don't be afraid to pick a carry if you're without one once everyone else has picked. Teams made up of only support heroes will struggle as the game goes on, and teams made up of only carries will be dominated early game. The key to victory is an effective spread of roles amongst your team that will keep you strong throughout.
Carry
Don't worry, I'll get us through this.
The Terminator enjoys destroying whole armies of robotic armies with his inhumane Austrian accent and his muscles (the size of my head). The carry of any game in Heroes of Newerth has the absolute same role. He will become the hero that will carry the rest of the team in the late game. There are hard carries, and semi-carries or soft carries. Either way, every team should have at least one of these bad boys.
I'll be back!Hard Carries
MagebaneSand WraithChronosThe Dark LadyPredatorWar BeastA hero is considered a hard carry when he has abilities that scale with items. The later the game gets, the more powerful he will get not only thanks to the items he can farm, but also through the ability that profits from items. These guys are the Arnold Schwarzenegger of the game. They come in with their shotties and wreck everything to pieces later in the game. They are the bane of every opponent's hero if farmed correctly.
Semi-Carries
PestilenceForsaken ArcherSoulstealerDefilerThese guys are more common among the many games. They are efficient earlier on but can't carry as hard as the others can. They like to go around ganking and getting kills more than hard carries but later on they won't be the Terminator level. They would drop down to an Arnold without as many steroids. These guys scale better with the end game items than most and can be quite devastating.
Support
The glue that holds a team together.
Honestly, the backbone of any team throughout the whole game. People can brag about how many kills they have or how many times they kicked ass in a game, but they are absolutely nothing without these silent protectors in the game. The support category would encompass most stunners and healers. These are the guys who don't go in wrecking everything, but rather make it possible for others to do so. They are the ones who usually watch over carries, buy wards and couriers, and all the things without which you cannot win a game.
Healers
Damn it man! I'm a doctor, not a carry!
JeraziahSoul ReaperDemented ShamanAccursedNymphoraAfter someone initiates a fight and the big guys show off their skills with their ultimates and showy skills, people start dying. These guys are what make it a lot harder for their respective teams to die. Rather than blowing off the heads of opponent's, they get to inject some steroids into their own heroes and watch them do the work.
Stunners/Slowers
You can run, but you can't hide.
Witch SlayerPollywog PriestSuccubusThey may not be the pow-pow-pow killers, but they do quite decently. They are part of the backbone of any HoN team. In most games, stuns create kills or prevent deaths. They are the guys you'd like to have in your lane in the beginning of a game, and the ones anyone would be scared to run at in a gank.
Initiator
Stick close to me and we'll make it through this.
TempestHellbringerKeeper of the ForestPharoahMagmusBehemothPeople like to throw around words like tank and such, but the real phrase for anyone who starts off a fight is an initiator. They don't have to be tanky, or very high health heroes but rather, they just need a skill or two that will be able to start off a fight with your team at an advantage. Heroes with this role normally carry a portal key to portal into the middle of the opponent team and work to AoE (area of effect) disable the opponent or give massive damage with a skill.
Tanks
Just tell me where to stand.
LegionnaireArmadonCorrupted DiscipleTorturerContrary to popular novice belief, a tank is not what he would be in a game like World of Warcraft. In the word of Simba, "Because Hon is not WoW." Take this to heart because it rings true. The players in Heroes of Newerth won't attack a player who isn't effective except to have outrageous health. They won't be polite and hit him for you, rather than dominate the weaker guys and ignore him. A tank is someone who mustn't really be extremely health-based, but will be better scaled for health items later on. The tank will be someone who doesn't die easily, but is someone that can't be ignored in a fight because of his damage output and health. You do
NOT NEED A TANK. They are absolutely optional, and not anything that is a must, rather just as nice addition.
Nuker
Well, he was there one second, and then he was gone.
ThunderbringerPyromancerTorturer
ARMAGEDDDDDONNN!!!Many people call them Glass Cannons in other games, but they have a bit more health in this game. They are exactly what their name implies, they are dropped and the whole team drops dead (maybe not all, but they're hurt.) Most of these guys are better at going around on a 1 on 1 basis, and making quick work of squishy opponents. They cause massive damage in quick combinations, and don't normally have too much health to survive. Use them to hide behind the steroid filled heroes, and chuck their skills at anyone unlucky enough to get hit by them.
Multi-Role Heroes
I've got what you need.
A lot of heroes can fulfill multiple roles but remain mainly concentrated on one. Still, some are very versatile and useful such as these:
Puppet Master - disabler/semi carry/hard carry
Pestilence - semi-carry/stunner/initiator
Deadwood - stunner/initiator/semi-carry
Pandamonium - stunner/semi-carry/initiator
Slither - initiator/slower/support
The Madman - semi-carry/initiator/stunner