The students tend to lose track of where they are in the role play and to become too inhibited to continue. I unobtrusively note significant mistakes that I hear and then elicit the correction of these errors after the students have completed their acting out. When practicing grammar structures, I find it hard to get my students to use complete sentences when I ask them questions. You can't really blame your students for using short answers, because they are imitating natural speech patterns. The only natural way to respond to this is with a complete sentence.
Intonation is defined as being a meaningful change of voice pitch within an spoken utterance.
In other words, it's the way we make our voice go up or down, usually at or near the end of a sentence, to show that we are asking a question, making a definite statement, expressing uncertainty, etc. The Ur book explains and describes different types of free speaking activities and gives lots of clear examples which you can easily use or adapt. It will help you to build up your own stock of activities. It's ideal if you need a good free speaking activity in a hurry. It's clear and pretty comprehensive.