SpoilerBlisstake hasn't actually rolled a check, to my knowledge. To speed things along, I've done that.
Tireas easily uses the roots and the rope tied to him to climb across the pit. Nothing gives way; evidently, the ancient tree above produces strong tendrils. The tiefling figures, based on his experience, that everyone else should be able to climb safely across.
SpoilerTireas knows it's a DC 5 climb check.