My tip would be to implicate the students more in their own learning by having them choose the debate topics and prepare for class before hand rather than doing homework afterwards.

For example have the students write quizzes for other teams of students to answer.
Quizzes can have a grammatical focus where they elaborate quizzes with the help of a grammar reference book, or they can be quizzes for knowledge - general or specific to topics your students work with or are interested in.

You'll find a lot more interest in class because students will be curious to see how others handle their questions.

With role-plays it's the same - students create spicy role-play scenarios for OTHER groups of students to act out.

You might also want to try my free games for teens and adults - just enter name and email in the top left of the page to receive them by email. There's a book of 194 games and activities as an option but I recommend that you try out quite a few of the free samples before you even considered getting the book to make sure that you like the style and find them helpful.

http://www.teachingenglishgames.com/adults.htm

Hope it goes well!
Shelley