'At risk' registers record details of young people and vulnerable adults who are deemed to be at risk from others around them. Such details are highly confidential. Even the class teacher of such a child, who is responsible for ensuring their welfare, is often unaware that their name is on the register. Such records would normally be securely destroyed once the child reached adulthood.
If your question actually refers to a register of offenders who might pose a risk to others then, again, such records are highly confidential and not publicly accessible. While police forces are now allowed to reveal certain information to the parents of a child who might be at risk (on condition that such information is not passed on to anyone else) the registers are not generally available.