Thanks for clearing that up. 4.1.3 talks about using one dice for 'game' rolls without being clear as to what a 'game' roll is, so that caused me a bit of confusion. I seem to have all three editions (for some unknown reason I kept the first rulebook) but I thought the third edition would have spelt it out.
"Game rolls" are defined in the "Using Tables" section in the List of Treasures in the Second and Third Edition. The section is on page 110 of the Third Edition [emphasis added]:
"5. USING TABLES
These cards modify how the characters use one or more of the tables in the game. They are in effect whenever they are active, and their effects are cumulative. Example: If a character has the Map of Lost City and the Map of Ruins active in a tile that contains both a Ruins chit and the Lost City chit, he subtracts two from his Locate rolls. Note: Die roll modifications do not apply to combat tables such as repositioning and changing tactics, or to game rolls such as the Monster Roll or Weather. These rolls are not considered to be character rolls. A character’s die roll modifications also do not apply to his hirelings; they use their own die roll modifications, if any."