Is it illegal to sell Bitcoin for cash?

It's official… selling your own legally acquired Btc to Paypal

 is a crime in the United States! If you sell your Bitcoin or other cryptocurrency without going through a regulated exchange, the US government is coming for you.

The answer to this question would also heavily depend on which country the transaction is occurring. Supreme court of South Korea ruled in July 2009 that exchanging virtual currency for real world currency is legal, even though doing so was against the game's terms of service.

First off, selling your account for real money is illegal and just plain scum bag-ery. Secondly, selling for robux or items is against roblox TOS and can get your main banned.