Laravel Built-In User Auth

I am using Laravel's Auth package for user registration and login. While registration, along with email, I have kept a roll_no field as unique.

Now when I register twice with the same email Id, it gives me a error message saying that this Email already exists in our records. But when I register twice with the same roll no, it throws a SQL Query exception (Instead I want an error msg similar to the case of Email conflict).

Please note that I'm using Laravel 5.1 I've surfed so many blogs and forums but they all answered for Laravel 4.2 There's some difference in these two versions. Thanks in advance

via Chebli Mohamed