This little hint/secret will help you with roughness or just plain BS when it comes to the Special Infected of Left 4 Dead 2:
Smoker - Constricts the survivor with his tongue, and can pull him back aided with the "help" of Common Infected. The easy way to beat this guy, is to shoot at him or his tongue when the animation of him pulling you starts.
Witch - A crying Teenage girl that has become infected and sees herself as unwanted. If you disturb the witch, prepare to pay for it with your life. The only real easy way to take her out, is to QUICKLY use a chainsaw melee weapon or a baseball bat up behind her repeatedly until she falls dead. If this strategy isnt taken, and you risk it, the witch will stop at nothing to see you dead, and she will eventually catch up to you.
Boomer - Vomits on the survivor with a strange bile that attracts a horde and can also blow up and spread bile. An easy and obvious way to take care of this guy is to push him back with your weapon melee and shoot at his belly from a distance.
Spitter - Spits an acid path out of mouth and spreads to a rough 6x6 area for constant damage. Easy way to beat this fella is to spot the green goo on its mouth when its far off or hiding and shoot at a strategical angle so that the spit doesn't hit you.
Hunter - Leaps at the survivor with hostile intent and starts slashing away for moderate damage. Beating these gus are somewhat easy if you have practice. All you have to do is dodge it's leap, and weapon melee it when you get the chance so that it is stunned and unable to attack.
Charger - Basically Charges at the survivor, carrying you a short - long distance until he slams you against a surface and pounds you into the ground repeatedly for moderate damage. There is no EASY way to beat a charger, but all i can reccomend is that when he charges, dodge it, so that he stuns himself and becomes vulnerable.
Jockey - Makes a small leap similar to the hunter (but more of a hop) and grabs onto the sruvivors head, yanking and twisting you in all sorts of directions for moderate damage. And easy way to beat the jockey is basically the same way you defeat a hunter, but be careful, because the jockey can get you even close range.
Tank - The Tank of almost every stage will appear at random. He does very high damage and knocks the survivor around like a doll until hes dead. He will also use a concrete - based range attack which will hit for moderate damage. Like the Charger, the Tank is not easy to beat, and doesnt really have a weakness. Most people, including myself, highly reccomend this: Just set it on fire, and run 'n' gun away from it.
I hope this helped. Use these strategies and you shouldnt fall victim to most of these attacks again.