Roguekiller is a legit program and you can download it from here
Most of the well known specialized tools we use as malware fighters are written by experts/Security Colleagues at various security forums like Bleeping Computer, TechSupport, GeeksToGo, SypwareInfo and other similar sites so they can be trusted
...this includes any program hosted by BC for download. Unfortunately, many of these tools are repeatedly falsely detected by various anti-virus programs from time to time. That sometimes results in an inaccurate site rating/warning of potentially dangerous software.
Rest assured our Security Colleagues are trustworthy and all the programs hosted for downloading here at BleepingComputer are malware-free and perfectly safe to use.