Rose Quartz (1)

Rose Quartz restores trust and harmony in relationships, encouraging unconditional love. Rose Quartz purifies and opens the heart at all levels to promote love, self-love, friendship, deep inner healing and feelings of peace.

Like most crystals, Rose Quartz can be cleaned in multiple ways. Placing it around other crystals, setting it in saltwater, and running it over water are some useful and convenient methods. 
You should clean your crystal if it were present during a negative event if it is new or you haven't used it yet if it feels weak or unbalanced and after rituals.