WPA-PSK is believed to be secure because the computing power needed to run through all the possibilities of passphrases is huge. Roth's conclusion is that cloud computing means that kind of computing power exists right now, at least for weak passwords, and is not even prohibitively inexpensive.
In other words, if your network relies on WPA-PSK, its time to check that passphrase. It's claimed that up to 20 characters are enough to create an uncrackable passphrase, but the more characters you can include in the passphrase, the stronger it will be. It should be noted that Roth very probably cracked open networks with short passwords.
Include a good variety of symbols, letters and numbers in the passphrase, and change it regularly -- monthly, if not weekly. Don't use words you might find in a dictionary, or any words that are constructed cunningly by replacing letters with numbers (that is, passwords like "n1c3"); hackers are way ahead of you on such "substitution" tricks.
Passphrases constructed like this are effectively impossible for computers to guess by brute force, even by cloud computing systems running Roth's software, due to the amount of time it would take.
Because WPA-PSK is also calculated using the service set identifier (SSID, or base station name) of the wireless router, it also makes sense to personalize this and ensure it isn't using the default setting (usually the manufacturer's name). This will protect you against so-called "rainbow" attacks, which rely on a look-up table of common SSIDs.
Keir Thomas has been writing about computing since the last century, and more recently has written several best-selling books. You can learn more about him at http://keirthomas.com and his Twitter feed is @keirthomas.