Well you need to seek legal advice, I know I have, to find out if their claim is legitimate, theres no other way around it, or you could find urself on more legal trouble, you need to speak to a trademarks attorney and it will cost you, but least you will know where you stand. They will let you know if that email is legal or not.
You could be right it could be fake but you need to make sure it isnt.
In the Uk someone has tried to trademark chatroulette too and chatroulette inc have objected to it, its not been trademarked by anyone yet.
Its all pretty confusing as if you want to get your software popular for the keyword chat roulettte you need links to it and also to mention it on ur site, but if someone gets the trademark passed, they can stop anyone they want from doing this.
Although when I spoke to my legal advisor, he said if chatroulette just turns into a general term then things could be different. As it could be argued that chatroulette is just the style of chatting and you could argue when you mention chatroulette you dont just mean their website you mean the word generally.
Its a potential minefield and does seem off you have got that email if the trademark hasnt been passed, however you need to make sure I wouldnt just ignore it, it might not go away.