I don't think you can really roleplay a character without a backstory. There would be nothing to roleplay with.
Even if your backstory is that they have amnesia and can't remember a thing before they woke up a superhero/villain one day, that's a backstory, and it would affect how you played the character.
However, I've never created a character I've been unable to come up with a backstory for. I usually end up making them, even if I didn't intend to. Velvet, for example, was created on Test originally, when the body scale sliders were first introduced. Maxed out chest and legs, tall, blonde. It was also when the martial arts jackets came out, so I decked her out in one of those, and thigh boots. Total [censored] with a katana. Five minutes of running around on Test, and she had a backstory (ex-Playboy model from Kent who had given up the business after marrying and having a child, now a hero to get revenge after her family were killed in a combing meant for a Family boss). She migrated to Union when I needed a character to play with while my main was busy out of town for a week or two, and turned out to be a nice character to play.
My current main, Nitoichi, was made with specific objectives in mind after I came back to the game. She was DB/WP because they were both new sets, and she was going to heavily involve herself with Vanguard, because of the RWZ revamp. I didn't have a backstory for her for maybe 5 minutes.
Edit: Also, as Syracuse says below, I pretty much never write down a ten page essay on my characters. Their 'backstory' is a rough outline of their history which gets filled in by annecdote while playing. (One of my characters is 8000 years old. If I had to write down his entire backstory I'd still be writing it.)
Disclaimer: The above may be humerous, or at least may be an attempt at humour. Try reading it that way.
Posts are OOC unless noted to be IC, or in an IC thread.
Jane was conceived as a concept more than a story, so to speak. It's a similar thing with all my characters, in all settings/games - the character develops over time based on his or her experiences, rather than anything I've already written down.
This approach has massive flaws to it, but at the same time it feels very organic and flexible to me.
Thanks Ravenswing. My main problem comes when i cant think of a story that works well with 'unsynergised' powers even for PvE, such as a fire/kin. Id love to get one to 50, but as i can never think of a story, I just cant be [censored] to level one 
Most likely seen playing Abigail in Black or Abigail in White
I can't play a character without a concept in mind. The backstory either falls into place or it doesn't. As for my actual biography box in game, it's empty on some characters as I'm lazy and forget to fill them in.
I simply cannot make a character and just play as a character in a game. They need to be 'real'.
Thanks guys. Maybe you will see me in PD with a drink in my hand
Most likely seen playing Abigail in Black or Abigail in White
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My main problem comes when i cant think of a story that works well with 'unsynergised' powers even for PvE, such as a fire/kin.
[/ QUOTE ] Kinetic control lets her vibrate molecules to cause ignition, allowing them to create and shape fire. They can also use their talents to increase their own speed and decrease that of others, weaken others to strengthen their attacks by inhibiting their momentum, and seal wounds together.
They can either gain their powers through mutation, specialized magic, some kind of piece of technology or other such sciency backgorunds, or they may just be naturally capable of that feat.
A backstory definitely helps me to stick with a character. The very few characters I have without backstories barely see double figures, even if I like the sets.
If you're struggling to find a good story, Mutation can be a good cop-out as it requires very little explanation, the powers 'just happened' and the person decided to use them for good/evil. Not very refined admittedly, and could look a little lazy but it can avoid lengthy explanations and get you out of a corner if you're struggling. 
@Dante EU - Union Roleplayer and Altisis Victim
The Militia: Union RP Supergroup - www.themilitia.org.uk
I come up with a concept I want, roughly, make the character, choose the powers costume etc. then let the backstory fall in about five minutes before RP. This probably shows. <.<
[Union Roleplayers]Kiken: Tick the off in your Observer Book of Lesbians
[Union Roleplayers]Nitro v. IV: we need a perma-man feature
[Union Roleplayers]Nitro v. IV: I'd trust you more if you did it in front of me
Gotta love dem dere RolePlayers
I find I often come up with complicated backstories, but they seem to iron themselves out or chnge almost against my will!
It's still fun though, just a little odd to see a character run away with itself.
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It's still fun though, just a little odd to see a character run away with itself.
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No, we had that discussion a little while ago. It's not odd at all. Rare is the person who discovers their character doesn't mutate in unexpected ways once played.
The biggest cases of this I have are both women. Velvet started out life as a driven vigilante [censored], and rapidly turned into a mother figure, possibly as a reaction to all the teens we had running about the statue at the time. Nitoichi, as she keeps telling people, was straight when she started out, and has ended up shacked up with another woman. I really didn't expect that. 
Disclaimer: The above may be humerous, or at least may be an attempt at humour. Try reading it that way.
Posts are OOC unless noted to be IC, or in an IC thread.
See! By the time you got to the end of that you were bemused too. Odd I say!
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I find I often come up with complicated backstories, but they seem to iron themselves out or chnge almost against my will!
It's still fun though, just a little odd to see a character run away with itself.
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It's exceptionally common, I don't roleplay but in my writing I usually find that the plot doesn't define characters as much as characters define plot.
My standard way of saying it is,
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Put the characters in the situation and let them deal with it, if it doesn't turn out the way you want it then adjust the starting variables (Hero is injured, villain is stronger, 6 instead of 3 minions, ect. ect.) until you get the desired result.
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I tend to work to this method, forcing characters to follow a plot that makes them act out of character (without good reason) makes you look bad as a writer.
I have an odd question...or more of a thought really. Im not a role player (Ive tried but I dont seem to get much further than buying a drink!) but I always write a back story, infact, if I can think of a back story, I delete the character! This tends to make my characters powers themed (eg Abi in Black is a fire,fire,fire magic using blaster). Do any roleplayers play characters without backstories, or do u do what i do and delete them if u cant think of one
Most likely seen playing Abigail in Black or Abigail in White