I found an ad that displayed a price of 600$ for two rooms. I was delighted because If I found a roomie it would be cheap rent. So I found a roomie and we each signed a lease for it. We asked the landlord if we split the rent and he said yes (while we were looking at the lease), so we signed. Now the landlord wants 600$ from each of us because we each signed a separate lease for 600$. Can I sue for some sort of fraud if I have the original ad?

I found an ad that displayed a price of 600$ for two rooms. I was delighted because If i found a roomie it would be cheap rent. So I found a roomie and we each signed a lease for it. We asked the landlord if we split the rent and he said yes (while we were lookin at the lease), so we signed. Now the landlord wants 600$ from each of us because we each signed a separate lease for 600$. Can I sue for some sort of fraud if I have the original ad?
Charging you both $600 doesn't sound like a split. What does it specify on the lease? One lease or two? I one of you leaves, will he be able to rent out the other room? I'd reread the lease and if it's not to late bail out on that landlord, NOW!

You both should have signed ONE lease that would have stated that you both tenants collectively responsible for the $600 a month rent. Instead the landlord had you both sign a leases saying you would each individually pay $600 for rent.

Its not false advertising but he is trying to scam you. I would try to get out of the lease.

Is it possible to get out of this lease though without getting sued by the landlord, or being responsible for compensation?

Most states have a "bail-out" clause, commonly three business days.
(editted)
My bad. I stand corrected. See post # 6

Most states DO NOT have "bail out" 72 hour/3 day recision time for leases... that rule applies to home loans on owner occupied properties.

Have a discussion with your landlord about your expectations.