RPG stands for Role Playing Game.
It comes directly from pen and paper role-playing games, such as classic Dungeons and Dragons or the British Warhammer Fantasy Roleplay (from Games Workshop's famous franchise).
It often includes Wargames mechanics, with a strong fluff wise story telling.
This genre was sadly rarely ported on Amstrad CPC, as Adventures games were far more common.
Contents of a proper RPG
A proper RPG shall include some kind GUI, and an evolution system for the player's characters.