RockSoc is the name used by the rock music clubs or societies at various UK Universities. The word is simply a shortened form of 'Rock Society' though many societies are officially called 'Rock and Alternative Society'.
Many universities and colleges in the UK now have a Rock Society, most of these are affiliated with the universities respective Student Unions which help organise, promote and fund student activities. They also offer insurance for any official trips and have the right to veto events if they deem the risk is too high.
These student groups typically hold regular rock music discos - where headbanging members can demonstrate their air guitar skills - and organise trips to rock concerts. Some also promote concerts of their own, often featuring members' bands. As well as rock based events Rock Societies are often known for putting on general events for their members.
There is also a UK-wide 'RockSoc' organisation which exists to promote rock music and provides links to the various individual Rocksoc groups. Although the various RockSocs are not formally connected in the eyes of the Students Union joint events are encouraged and funded making them official events despite the lack of connection.