A roflconda is a large, snake-like creature consisting of many Creeper heads. The sick and disgusting name given to them by the wizards who created them by meshing many creepers together into a snake-like being references the way that the wizards would laugh when they blew up and killed people -- these sick and insane mages would literally fall to the floor and roll around in laughter. These eldritch beings are quite dangerous and pack an explosive wallop.
The wizards realized creeper explosives are packed into their heads, so they took many creeper heads and made them into a living snake. This means that they make much bigger explosions than creepers.
Only their front heads take damage, so make sure you are aiming well when you hit them. It's easier for warriors to melee their heads because there's no distance involved.
Individual Roflconda explosions aren't powerful enough to one-shot a Mage of similar level. Multiple Roflcondas, however, can pwn you, so be careful.
Like the Creeper, the Roflconda will become "supercharged" when struck by lightning, doubling the power of its explosion. Since rare spawn Creepers and Roflcondas already have double the base explosive power, supercharging one will result in quadruple the fun...
Because of dirt's temporary role as a repair reagent and it's low resistance to explosions, it can be beneficial to have a Creeper or Roflconda explode near you, using the ensuing rubble to replenish your gear.
For some reason, the normal creeper (and to a lesser extent, Phase Creepers) can sometimes be quite rare. But the Roflconda seems to be all over the spawn rate in quite a lot of worlds, likely because they are the favourite creation of the dark wizards who spawned them into the world. The lack of normal creepers is probably related to this as well, because several creepers are killed to make one roflconda.