Rondos can be used for most elements of the game and I often use them to start off a training session.  While a rondo can simply be used as a warmup activity to work on 1-2 touch, it can much more effective if related to a moment or tactic of the game.  Rondos offer you an opportunity to start to bring our your sessions topic first with small numbers/relationships, before progressing to the larger grid and adding more lines/combinations of players.