It's a reference to either:
1. A rocket launcher
2. A helicopter
But also can be used for fun.
Helicopters make a soi soi soi kinda noise so saying pharses like the one in the example explains it, the rofl is added on just to make it seem kiddish and funny.
Eg. My Roflcopter goes soi soi soi soi soi (as you spin around with a rocket launcher or just because helicopters make a soi noise)
Invented by a Blizzard moderator on the Warcraft III forum. There is always much whining going on on those official forums, much sucking up to moderators and an awful lot of 'BLUE!!! PLZ REPLY!!!1one' (Blue = color of moderator posts), so when a mod posts something, you can bet there'll be thousands of people jumping on it, if only to spam 'BLUE FIX GARGZ PLZZZZ' or 'first reply woooot!' after it in the vain hope that the mod will read it and react.
So when one invented this new buzzword, it was grabbed and squeezed out and spread like a virus across all of the Blizzard forums and from there over the internet.
The word is derived from a unit in Warcraft III, the gyrocopter (flying machine). Your immediate response when someone masses gyros (to be funny, ruin the game, mess around or whatever) is to rofl for ten straight minutes until the copters of doom and destruction have pinpricked 1 of your 20 farms to death with their uber godly bombs.
Now mostly used in Blizzard circles as a leeter version of rofl.
'...and this guy said I could reduce lag by up to 100% by hitting alt-F4. I did and the game closed on me. This is griefing, admins plz ban'
The superior being of chatspeak, 'roflcopter' out takes down all lollerbladers, lmaoplanes and various other outlawls. Pilots of the roflcopter often enjoy a nice crispy ZOMGBBQPIZZA and some lolmonade. Children also enjoy a good ride in the roflcopter, as it spreads smiles and festivals known as the 'lolapalooza' across the world.
Captain Sloloman of the elite omega roflcopter squad enjoyed a fresh ZOMGBBQPIZZA and a cool lolmonade after his swift victory over the lollerbladers, lmaoplanes and outlawls and returning safely to the lolapalooza.
......<ROFL ROFL ROFL ROFL>.
..\ \_...........|--|---|..\\ ....\....
../ L \____,/-------\___\___\
..\ L /______,---''-----------, /...
../ /.............\_________ ,/....
'i tripped on my lollerskates'
The ASCII helicopter that brings joy and god laughs to children everywhere.
The Rofl Copter visited me yesterday and I laughed so hard I rofl'd
Roll On Floor Laughing, Can't Operate Properly Till Eyes Refocus
We ROFLCOPTER at you, when you try to eat cheese and crackers with chopsticks
acronym meaning "Rolling on floor laughing can't operate properly till eyes refocus"
when you physically find yourself laughing so hard you begin rolling on the floor making helicopter noises and moving the motion of a copter
Alexandra:hahaha dude what are you doing on the floor?