Here are some internet games that help students learn about the root words, prefixes and suffixes:

Skillswise Rootwords: You can choose entry, average or difficult level. In addition to the game there is a fact sheet with definitions, a quiz and a worksheet that can be printed out.
Fish Tanks — This site helps you spell words which have a prefix and a suffix added.
First School Years— This site has many printouts and quizzes. There are also links to other subjects.
TV411 Vocabulary (1)— This game allows you to choose a prefix to a word.
TV411 Vocabulary (2)— This game allows you to choose the correct suffix to a word.
Quia Roots And Prefixes— This site uses the concentration game to teach the definitions of prefixes and suffixes.
Flamingo game— Adding the suffix y or ly
Crystal Castle game— A castle is built as you add the correct prefix to a word.