I was more thinking about circumstances I've heard e.g. Jizzler 700 confirm you have information Golf? in which case it seems Roger would not be the appropriate readback.
"Roger" would
certainly not be the appropriate response. The word is in the aviation lexicon to enable a person to convey that he or she has received the whole of a transmission rather than reading back the lot. It's there exactly because some ATC/S messages contain a mixture of readback items and other information and it helps ATC/S to know that the whole of the message has been received. Often the other information has been included so as try to avoid having further, unnecessary communications.
It's confusing, and as a weekend warrior I daresay the AIP or VFRG isn't laid out best to help educate pilots on the proper radio phraseology.
It is also a subject matter that is seemingly entirely absent from the PPL/CPL syllabus - at least in the theory exams, not the flight tests.
Agreed, and I'd hazard a guess that we're not Robinson Crusoe. Most of it's been left to people's own devices and that's why there are so many differing practices.
(I do hope someone 'in the know' at YSCB can explain why I have to readback a QNH that is already contained in ATIS information which I've already reported as having received.)