America's Army/Flash Grenade

This is the most underrated weapon in the game. The flash will completely blind and incapacitate anyone within its radius without risk to civilians. The ROE penalty for the flash is -5, so if there is a friendly surrounded by a ton of enemies, and you are sure that you can get all of them, flash them all, and you have about 15 seconds to kill all the enemies. Keep in mind that this grenade only has a 1-2 second fuse, so DON'T COOK IT.

''In my experience, the fuse is more like 3 seconds. When using a flash, I usually cook it for one second then toss, so that it explodes in mid-air, not on the floor.''

At the most, just pull the pin and throw it right after. This is as dangerous as a Frag, because it takes a player out of action for over 15 seconds, leaving them helpless. It also never gives an enemy time to run for cover. If you see one land near you, there are two things you can do. The first is point your weapon in the direction that your enemy will probably come from and start firing a moment after you are flashed. The next is to look in a direction that will lead you to relative safety, such as around a corner, and start running. Continue running until the flash wears off a little.

A [STX] Zealot AA Guide
"In my own experience and tactics I find it best to do the following if you find an enemy flashbang. First quickly turn away from the tossed grenade and point your gun at the floor. This will lessen the effect on your sight a little, but enough to still be able to see and fire. Now you must do one of 2 things, attempt to take out the OpFor enemy OR the better option run for cover until the effect completely wears off. This will allow you to stay safe and ready for battle when a flashbang comes your way again."

There is already a great post about the flashbangs and how to use them, but the following is specifically about rolling the flash. Never cook a flash when rolling. Rolling flashbangs creates a huge advantage when you are standing next to the door you want to enter. Instead of throwing the flash and having it bounce to a corner or behind an object where its effects are diminished, by rolling the grenade at the foot of the door (where is where that sneaky OPFOR is looking.. I promise!) it will stay in the doorway and explode there instead of in a stupid corner where nothing happens. Also, when rolling a flash you really can't see it when it goes into the room because it is so close to the floor, giving the OPFOR a less amount of time to react and turn away from it.

If you toss it, try and angle it so their is an object between you and it, as the short fuse makes it easy to get hit before you have a chance to run, and nothing says easy target like a blind soldier, especially when the give themselves away with actions like running against a wall.

What to do when you get flashed
Crouch and stay immobile until flash wears off. Your other options are:
 * Try to remember the direction where the flashbang came from, wait a few seconds, then open fire.
 * Pull out a frag grenade and leave it cooking in your hand. Do not throw. Essentially you commit suicide, but there is a chance you will bring the enemy along with you.
 * Try to run away.