Well! You have only your DM to blame, then! The roper SHOULD kill you if you're a bunch of upstart young whelps who can't figure out how to save your own necks! As stated in the module text, the roper encounter is there to TEACH THE PARTY A LESSON IN HUMILITY.
I DMed this module, and liked it (though I'm enjoying running module #5 in the series so much more). The roper encounter was great fun: I wish I could post the details, but I'm sure that would spoil someone's fun. Let's just say that roleplaying a roper eating a donkey tops the chart of my recent experiences.
As for the dragon encounter, I think it is excellent, and quite well-balanced. The party I DMed had absolutely no idea that there was a dragon down there. There were also five 4th-level characters in the party, and it definitely helped that one of them was a ranger archer with Dragon as favored enemy. The only softballing I did was being sure to spread the pain around. There was plenty of hit-run-and-hide in there, and the party had a memorable encounter. Stupid monk and wizard jumping around on a pile of treasure is sure to draw ire from dragon.
At any rate, I am happy with the way I ran the encounter, and happy with the way the party killed the friggin dragon. Even after they had learned to run away from or bargain with Big Scary Bad Guys like the roper.