Even back in the days of the 3e adventure, that Roper was a party killer. I think when I played, only one of the party of 4 survived.
I threw a roper at my party a couple years ago when they were about 5th or 6th level and it was surprisingly effective. I think it's an underrated monster.yeah, I see why. The combo of the environmental danger of the river amps it up too.
My encounter was a roper on the ceiling, surrounded by a ring of piercers, with a trapper on the floor. The roper and trapper were a meatgrinder, but the piercers were mostly useless.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.