I'm not sure what you mean by roof terrace, but is it open to all sorts of people? Is it safe for the Bun? He should definitely NOT be kept there unsupervised, he could get very hurt... try to get your BF to sit down with treats and gently coax the bunny over. After a while waiting, a well-socialized Bun will come to almost anyone... especially for yummy treats try yogurt drops (in pet stores), dried cranberries, carrots, parsley, apple, etc.