I wrote about how I like bad guy rosters, and Douglas Cole wrote an excellent post about making them.
Benefits of a Keyed Monster List
Being Doug, it's thorough and has pictures and variations and expands on the idea.
This leads me to my main comment on this all: Try different versions.
For me, I like a spreadsheet. I don't bother with the nearby rooms of Doug's "neighbor" column, nor do I do a relationship map. After all, I have a map and I know what's in each room. Even if I don't, because it's someone else's dungeon, I'll do the homework and learn it. Having a map and a spreadsheet and a relationship map is more than I need to function. In fact, it's three places to find two pieces of information (who/what, and where). Even a keyed "this room is near rooms X and Y" type list on a spreadsheet means two places I can look, but also two places I need to make sure are correct. I just need the one spreadsheet so I can cross out the dead all in one place. Yeah, I'll go back later and adjust my adventure key, but during play I just need one area to track things.
Putting lots of information on a roster can be a good idea if you have a lot of prep time. You can always ignore what you don't need. With experience, you can always winnow it down to what you actually use all of the time. Mine tend to have room key #, HT, HP, weapon, and notes plus a side note with weapon damages. It's all ready to go for me.
Knowing how you use tools is critical. When I first ran B2 The Keep on the Borderlands for my DF game, I downloaded a copy of the notes-on-the-map "Better Caves of Chaos" by Zak Smith. It's really cool looking. I thought it would help me. It didn't. I work better and faster with a keyed list and a map with only physical notes on it (X-ed out broken down doors, marks for pits and puddles, etc.*) Visually some things work for me, but others don't. I need more than just notes on a map, and once I need more than just notes on the map I may as well fully move those notes on the map elsewhere and just use that.
I tried a map with monsters listed but that's not how my brain likes information organized for use. Lists and maps, yes. Maps with notes on it saying what monsters are where? No, that's messy to draw and messy to use for me.
Relationship maps? Yeah, for me, they are great for relationships, not for where monsters are. I have one for the various Felltower factions. I don't really use it. I haven't updated it. I don't really need it, I just did it to organize my own thoughts visually and make sure I didn't miss anything. If I was publishing Felltower** I'd have to organize it so others could use it. For me? Nope, although it was useful as an exercise. I use my sideview map more, even if only to think, "I wish those guys would find their way to level 8, I had that great idea in 2011 and it's still waiting to be found."
It's all about how you personally most beneficially organize and use information. I know what works for me and what doesn't because I tried them and know which ones got shunted off to the side when the dice hit the table. Doug's post covers a few different ways to deal with rosters and understanding of the inter-relationship of monsters so you can have them react (either to dogpile or run) or influence the PCs appropriate . . . and with all of your information at your fingertips in the form you need it in.
* Marking hearing distances from major areas can be useful - if you have an alarm gong, marking how far it's heard can help (hint - sound doesn't travel in a uniform radius around a point in tunnels blocked here and there with doors.) GURPS Underground Adventures has a useful way of figuring this out.