Hm. Regarding sources then...
I derive mafia role ideas from a variety of sites, primarily among them Smogon. I've also used stuff from epicmafia and mafiascum. In terms of stuff from Smogon, I have 19 complete post games and role lists backed up to word documents on my computer, for new games and old ones alike, to aggregate experimental concepts and data. That's also why I spectate on smogon; I watch every active mafia game from start to end, every day, to see who dies and how. I have personally spectated every game since Nintendo Mafia, I believe. That was about when I started mafia in private communities, and I turned to Smogon for ideas. I picked up postgames from some old games too, with more experimental concepts (the original Viva, MGS, and Unicycle postgames, among others). (I have friends who actually do stuff on Smogon, like the Pokemon metagame, and they've told me that a lot of Smogon mafia plays out on IRC, which I totally realize. However, there's a lot to be found in just the forum threads even.)
I've also hosted mafia games of my own; two to be exact, and my friends and I have come up with some weird roles for them. (In all honesty, the balance was missing from the games I hosted. The concepts were there though.) If you're wondering about any specific roles, chances are I can recall where i read them from memory, so feel free to ask.
I tend to be a bit over-systematic when I write categorized documents like this though, so a lot of the names might be different. The descriptions (of which there are a lot, I'm afraid) are the reliable parts, I think. For example, I call hooker roleblocker, but the two roles are really the same.
The priority order I list them in is what I find the most natural, but obviously priority is up to the host. Since I emphasized priority in the ordering, some actions get their own entries when they really are part of a prelisted role, and I only separate them because the priority is different. (I grouped all the kills priority-wise, for example, so the bomber kill is separate from the bomber's main role action.)
For example, rolewarder came from DotA Mafia's goblin techies (blue_light). Nexus came from epicmafia, I'd bet. Same with some of the other ones like Party. I blended watcher and tracker into spy, although information is relevant to them both.... the list goes on. The bomber role was partially inspired by a game I hosted; I forget the other role that it came from. Probably also the goblin techies. Assassin came from roles such as Seviper in Raikage's pokemafia. Selfdestruct, from roles like Voltorb (I believe in the same game). Recruit partially comes from epicmafia (or was that mafiascum?)'s yakuza role, and partially from some stuff I came up with myself. Etc. All the above are from memory. I put a lot of time into this (considering its mass, that's probably self-evident), so I can remember writing most of it.