TamilRockers is essentially an unauthorised pirated website used by individuals to download their favourite movies and entertainment. Since the website is banned by the Government of India, it is unlawful for any material accessible on the website to be accessed by accessing the website.
If you even enter the website and get caught by some such unlawful means, then you might have to face penalties for breaking government officials' anti-piracy rules.
It is suggested that you not use pirated websites of any kind since you are responsible for promoting and maintaining those websites.
The website also appears to have no rights over the material that has been submitted for uploading by users. Your anonymity, as well as sensitive knowledge, will unknowingly be at risk if you access those pirated websites over the Internet.
Thus downloading from TamilRockers is illegal and vulnerable.