I've only ever used a conical roof once (and that was some time ago) but I'm pretty sure I used the roofslopeangle cheat to modify the height. Hopefully someone more knowledgeable will be along shortly to give you the definitive answer.
You can change the roof angle of conical roofs, yes, but if you want to change only that roof, you'll need to use the individualroofslopeangle cheat. It came with Pets; not sure if it was carried through with later EPs. Or you can use the M&G slider Zandvoort mentioned, if you have M&G, but then you're stuck with whole numbers and a smaller allowed range of angles. Me, I will often have roof angles like 28.724816... to get them to line up JUST SO with another section of roof. You can only do that sort of thing with the cheat-window commands, not with the M&G slider.
So I'm taking another stab at documenting a neighborhood. This one stars Benjamin Long. Pathetic attempts at humor can be found here.
Also at that LJ, there's stuff to download, some of which aren't/won't be here on MTS.