The terms roleplaying and psychodrama have some overlap, but they refer to slightly different things. The difference is important for trainers, since roleplaying is a more suitable approach for training, and it is possible for roleplays to stumble into the realm of psychodrama. That's problematic because psychodrama should probably only be used by trained therapists or other mental health professionals.
Roleplaying simply refers to any activity that involves taking on a role and enacting behaviors related to that role. For our purposes we consider it to be a training tool.
Psychodrama has different roots, since it's embedded in therapy and counselling models and tends to involve more emotional aspects, and to be more intense. As a result the debriefing of the process is more complex and requires advances skills, and debriefing is more oriented towards feelings and emotions rather than skills.
It is important that trainers know the difference between doing therapy and doing training, and when "pretend" activities become too emotionally laden, that line starts to disappear putting participants at risk due to emotional stress, and also putting the trainer and the organization at risk due to liability issues.