It means angry, furious, in a bad mood. Perhaps it is more of an Oz and NZ saying.
Cheers
KHP
Yes, agree, I am born and bred New South Wales, rural districts. My immediate family use the spelling 'ropeable' and they explained it to me as 'becoming so angry they need to be held back as though anchored down by ropes' I asked about what makes it different from being 'irrate' or 'furious' ... well :

someone inadvertently spills a jug of milk ... its the last drop until the milk gets delivered tomorrow ... you are 'irrate' because there's no milk for your visitors who will arrive later today.

someone knows there are visitors due later today, but still pours himself/herself a full glass of milk, using it all. You are furious at their lack of consideration.

someone, when asked 'who finished the milk' stands up and postures and says 'what's it to you ... you're not the boss of the ....fridge and grabs the fridge door, swings it wide open, and slams it shut so things in fridge are heard to fall, shatter etc.... well ... that is when both the questioner and the milk drinker are ropeable and both need to remember to act with restraint or be ' whalloped to kingdomcome and back'
JM