Let us take some example.

          Roster form                                     Set Builder form 

1.       {1,3,5,7,9}                                      {x| x is an odd number less than 10}

2.        {2,4,6,8}                                        {x| x is an even number less than 10}

3.        {a,i,o,u,e}                                      {x| x is a vowel in English alphabets}

4.        {January,June,July}                         {x| x is a month whose name start with letter J }

In this way we write Roster form in set builder form.