the easiest way to do this, is to use a boggle solver such as: http://www.danvk.org/boggle.php
Just put in all of the letters in the game, then it will find the possible words.
Obviously, you will want to input the longest word, which should appear at the top of the list.
** Sometimes in Wordament the game will include double letter tiles such as (ch) or (er) etc. These can't be inputed into the solver so avoid these rounds. **