The OP is preparing for the Comms exam (and presumably if in the UK) the practical test. Careful study of CAP413, chapter 2 is required to understand the definitions attributed to these words. The word 'Roger' has never implied that any action is going to be taken. Capter 8 is required to appreciate the format of any distress call.
Although the desired format of the distress call is aimed at the unit with which you are already in communication, it may be that at low level that agency might not be able to hear the call. Therefore any other aircraft on the channel ought to be ready at any time to relay the message.
TOO