DC15 Athletics please. You move at half speed down the rope and there are 16 squares, so for the sake of argument, I'll call it four rolls each. If you fluff it by more than 5 you fall. Actually, I don't think any of you CAN do that badly, but you might.
Fretting about the ropes serves to distract the party from their immediate problem. Whether or not to advance down the narrow tunnel. Two can fit abreast, but it will only be possible to crawl, so low is the ceiling.
Welcome back! ^_^ ...in other news: we had to connect the Flying Hook to the Rope of Climbing to get down here, didn't we? Which means that we wouldn't be able to reach back up with just one of them. :(
"...We may want to leave the ropes here for now? Do we know if that path has a way out?"
"I mean, I'm stuck with you all either way. If you think it's a good risk, I'll do it. But I really don't want to be stuck down here without something tricky.
I'm Anri's Player, and I approve this marching order. ;D
To put you all out of your rope-obsessed misery (and it is well-worth hanging onto that flying hook and the Rope of Climbing), you will be able to retrieve them both. Whether you want to do that now is up to you.