Since keys now last 7 days....
Melisande keys are mind-numbingly easy - just a little slow from having to wait for the dryads to reset. That time, I usually spend killing coil or thrasher (the latter for the leather), though my cu can do hydras, and maybe even abscess itself (but only if nothing else hops in), solo.
Dreadhorn keys are a pain in the rear, though I actually like hunting them. It's usually too much work for a 5-10 minute group fight. my cu's actually beaten guile, irk and spite in a 3 vs. 1 fight (the spiders are the real issue).
After spending the better part of 6 hours trying for parox keys, and fighting the Putrifier for 5+ of them with no key, it's definitely not worth the effort.
Grizzle keys are apparently child's play for my buddy's sampire, not so much for me or others.
Travesty keys are easy if you know what you're doing, but they are worse than Mel's keys in terms of waiting out timers, and drop slowly.
The Roof is painful for other reasons (not the least of which is the devs not having a clue about how that system really worked, and they broke more than they fixed)
Alternatives are fairly straightforward (but you have to be willing to get ToL if you weren't here for it being given out free).
- There's non-Fel champ spawns, especially the Dragon Turtle. What high-end new items didn't come from the Roof came from the Turtle.
- T-Rex is a fun hunt and has ok loot.
- Find a group of non-spawner players. When dealing with non-timer-based key carriers, you can get a lot more if you are farming all of them at once (of course, this doesn't work for Mel, and with Travesty only partially (3 groups of hunters, all waiting out timers)). UO is an MMO, not a single player RPG.