So it is with a song in my heart and a massive credit card charge that I can say that my roof is now in better shape than it has ever been during my entire tenure here in this silly house, and probably than it has been in the last twenty years...
Here's the bastard skylight that WAS up there:

...note the complete lack of anything resembling a waterproof seal on the low end; the idiots who owned the house before me all independently decided that the leak MUST be on the high side, and wasted a lot of time putting layer after layer of tar goo all over it; it wasn't until I got up next to it on a ladder from the inside, and saw that, lo, the metal on the bottom was almost completely rusted away, that the truth came out. Fast-forward through many months of having a tarp duct-taped over it, and finally this piece of shit is off the roof. I am going to give it to my mom to use as a cold frame. Woohoo.
Because the roofers discovered the extent of the damage only after they took this thing out, this was their temporary over-the-weekend solution:

That would be a half-sheet of plywood (which I paid for, even though they took it with them when they left) and a crapload of tarpaper (which accounted for my being billed for another 1/2 roll); it looked like this from the ventral side:

Note the massive hole where the plaster and lathe had been slowly rotted away over a span of years... the floor below, which is over the main bathroom, is so water damaged that I'm going to just use it as a tile substrate. Luckily, this room was a full bar when I bought the house, and so it shall be again, only this time, I am designing it. Which basically means it'll never get done, but whatever.
So this morning they came back and finished everything up; here's what the inside looks like now:

And here, at long last, is the new n' improved exterior:

Sooooo much better. Also, it has a vent, which provides a glimmer of hope that, when summer finally arrives, one will not immediately burst into flame when ascending to the third floor. Yay!
So, even though I ended up spending about a thousand more than I intended to spend, the fucking thing is finally done, and I basically have a new roof out of it; here's a good view of the edge of my roof (with the other, less leaky skylight) and my neighbors' free roof repair:

Pretty much that entire edge was completely degraded and allowed water infiltration, as did that far top edge (the parapet); it actually doesn't matter how expensive this was,
they did a great job, and I would enthusiastically recommend
them to anyone. I just wish I wasn't so damn broke.