They're actually a lot easier now. As BGlave said, it was once almost impossible to get signets due to the massive fluctuations in price of the keystones, terrible drop rates (signets and keystones) and also the fact that it was almost impossible to get a world where the boss rooms weren't crowded.
As for camping Roarius's, my personal preference is not to. They are the easiest to kill in terms of level and HP but they can quickly exhaust food/potion supplies as they're rather accurate with their attacks. I've also found their drop rates of keystones to be poorer than that of the higher level monsters.
As for gear and stats I'd recommend not using degradable armour or weapons while collecting keystones. The dungeon is multicombat and most of the time you end up fighting 2-3 monsters at a time. As for the Legiones, use the best gear you can also boost your HP as best you can.
If you're doing it with a partner you should get quite a few boss kills per trip. Hope that helps and good luck with it.
Edit: The drop rates for Signets seem to be about 1/64